High Court of Australia Gibbs C.J. Mason, Murphy, Wilson, Brennan, Deane and Dawson JJ. W v W [1982] HCA 73 ORDER Order that the question asked in the case stated be answered as follows:—Question: Has the Supreme Court of New South Wales jurisdiction to entertain the proceedings in that Court and to make the declarations sought in proceedings No. 4292 of 1981? Answer: No. Cur. adv. vult. The following written judgments were delivered:— Dec. 16 Gibbs C.J. The question which is raised for decision by this case stated is whether the Supreme Court of New South Wales has jurisdiction to entertain certain proceedings brought in that court and to make the declarations and orders and give the directions sought in those proceedings. The proceedings in relation to which the question is asked were commenced in the Equity Division of the Supreme Court by D.M.W. and R.C.H. as plaintiffs against C.G.W. as defendant. In those proceedings the plaintiffs claimed as follows: 1. A declaration that the plaintiff R.C.H. is the father of the child K.J.W. born 4 October 1973. 2. A direction that the defendant submit to a blood test for the purpose of ascertaining whether the defendant is the father of the said child. 3. An order that the plaintiffs have the custody of the said child K.J.W. 4. An order that the defendant pay the plaintiffs' costs in these proceedings. 5. Such further and other relief as to the Court may seem appropriate. The defendant opposes the order sought. D.M.W. and C.G.W. were married on 9 June 1966. On 4 October 1973 Mrs. W. gave birth to a female child, K.J.W. On 31 October 1980 Mrs. W. commenced to live with Mr. H. and on 7 November 1980 Mr. W. issued an application for the custody of K.J.W. On 28 January 1981 the Family Court ordered, in proceedings brought by Mr. W. against Mrs. W., "that until further order of the Court the husband have the care and control of K.J.W. the child of the marriage on an interim basis". Further orders were made giving access to Mrs. W. No appeal was brought from that order and the Family Court has not varied or revoked it. Subsequently Mrs. W. applied to the Family Court for dissolution of the marriage. The application alleged, but the husband's answer denied, that K.J.W. was a child of Mrs. W. and Mr. H. On 4 December 1981 the Family Court pronounced a decree nisi for the dissolution of the marriage. The Court noted an undertaking by the husband and the wife to do all things necessary to give effect to the provisions for the care and control of K.J.W. contained in a document which bore the heading "Consent Orders", and which dealt with the care and control of the child during a period which ended on 1 February 1982. Mrs. W. married Mr. H. on 9 December 1981. The proceedings in the Supreme Court were commenced on 4 December 1981. That part of the cause that raises the question now asked has been removed into this Court. There is no doubt that the Supreme Court has jurisdiction to entertain the proceedings brought in that Court, and power to make the orders and give the directions sought in those proceedings, unless either the enactment of the Family Law Act 1975 Cth, as amended ("the Family Law Act "), or the making of the interim order by the Family Court, has in some way divested the Supreme Court of its jurisdiction. Power to make a declaration of paternity is given to the Supreme Court by s. 13 of the Children (Equality of Status) Act 1976 N.S.W., as amended, and power to give a direction for the use of blood tests is given by s. 19 of that Act. Power to make orders for the custody of an infant is given to the Supreme Court by s. 5 of the Infants' Custody and Settlements Act of 1899 N.S.W., as amended, although the Court already possessed an inherent jurisdiction to make orders for custody. The combined effect of ss. 8(1)(a), 39(1) and 40(3) of the Family Law Act, and of a proclamation made under the last mentioned sub-section on 27 May 1976, is that since 1 June 1976 proceedings of a kind referred to in pars. (a), (b), (c), (d), (e) and (f) of the definition of matrimonial cause in s. 4(1) of the Family Law Act may not, with immaterial exceptions, be instituted in the Supreme Court of New South Wales. Such proceedings may be instituted only in the Family Court. The only kinds of proceedings with which we are concerned in the present case are those referred to in pars. (c)(ii) and (f) of the definition of "matrimonial cause". Those paragraphs read as follows: (c) proceedings between the parties to a marriage with respect to (ii) the custody, guardianship or maintenance of, or access to, a child of the marriage. (f) any other proceedings in relation to concurrent, pending or completed proceedings of a kind referred to in any of paragraphs (a) to (e), including proceedings of such a kind pending at, or completed before, the commence ment of this Act. The proceedings between Mr. and Mrs. W. were of course proceedings between the parties to a marriage, but they were not proceedings of the kind referred to in par. (c)(ii) unless K.J.W. was the child of Mr. and Mrs. W. In the ordinary meaning of the words, a child of a marriage is a child whose parents were the parties to the marriage, or perhaps a child who has been adopted by the parties to the marriage. A child whose father is not the husband, but a stranger to the marriage, is not a child of the marriage in the ordinary sense of the words. Section 5 of the Family Law Act makes it clear that the words "a child of the marriage" are used in the Act either in their ordinary sense, or in the extended senses given to them by the deeming provisions of s. 5. By s. 5(1) a child adopted since the marriage by the husband and wife, or a child of the husband and wife born before the marriage, is deemed to be a child of the marriage for the purposes of the application of the Family Law Act in relation to a marriage. Section 5(1) has of course no application to the present case. By s. 5(1)(c) of the Family Law Act in its original form, for the purposes of the application of the Act in relation to a marriage, "a child of either the husband or wife (including an ex-nuptial child of either of them and a child adopted by either of them) if, at the relevant time, the child was ordinarily a member of the household of the husband and wife", was deemed to be a child of the marriage. This section was amended in consequence of the decision in Russell v. Russell [1] , and by s. 5(2)(b) of the Act in its present form such a child is deemed to be a child of the marriage, but only for the purposes of the application of s. 63 in relation to a marriage. K.J.W. appears to answer the description in s. 5(2)(b), and is therefore deemed to be a child of the marriage for the purpose of s. 63 of the Family Law Act. That section has no bearing on the present case, and K.J.W. is not deemed to be a child of the marriage for the purpose of par. (c)(ii) of the definition of "matrimonial cause" or for the purposes of ss. 61 and 64, which empower the Family Court to make orders for custody and access. It follows that if K.J.W. was a child of Mr. H., the proceedings between Mr. and Mrs. W. with respect to the custody of K.J.W. were not proceedings of the kind described in par. (c)(ii) of the definition of "matrimonial cause" and further that if proceedings had been brought by Mr. H. in relation to the proceedings between Mr. and Mrs. W., the proceedings brought by Mr. H. would not have been in relation to proceedings of the kind referred to in par. (c)(ii) and would therefore not have been proceedings of the kind referred to in par. (f). 1. (1976) 134 C.L.R. 495. In these circumstances it is not necessary to consider whether the Parliament has power to make laws empowering a court to make orders for the custody of a child who is a child of only one of the parties to a marriage, and who has not been adopted by both spouses. The power of the Parliament under par. (xxii) of s. 51 of the Constitution, to make laws with respect to "the custody and guardianship of infants" is not expressed to be limited to children of a marriage, but it may be exercised only in relation to divorce and matrimonial causes. The power given by par. (xxi) of s. 51, to make laws with respect to marriage, does, as was held in Russell v. Russell, enable the Parliament to declare and enforce the rights of the parties to a marriage with respect to the custody of the children of the marriage, quite independently of the existence of any proceedings for divorce or any other matrimonial cause. The actual declaration made in that case, so far as it is presently material, was that s. 39 of the Family Law Act was a valid law of the Commonwealth in so far as the jurisdiction conferred related to par. (c)(iii) of the definition of matrimonial cause contained in s. 4 of the Act as it then stood, "but only in so far as it relates to proceedings between the parties to a marriage with respect to the custody, guardianship or maintenance of, or access to, the natural and adopted children of the parties to the marriage" [2] . In conformity with that decision, the definition was amended to put it into its present form. Even if it were assumed, notwithstanding the decision in Russell v. Russell, that the Parliament has power to make a law conferring on the Family Court jurisdiction to entertain proceedings between the parties to a marriage with respect to the custody of a child who is not a natural or an adopted child of the parties to the marriage, that power has not been exercised by the enactment of the Family Law Act in its present form. 1. (1976) 134 C.L.R., at pp. 556-557. For the reasons I have given, the jurisdiction of the Family Court, so far as the custody of children is concerned, is limited to children of a marriage. Clearly that Court has jurisdiction to determine the existence of the fact on which its jurisdiction depends — e.g., whether a child is a child of a marriage. However, it is not competent to decide that question conclusively. Indeed, the Family Court could not be given power to decide conclusively the existence of a fact which, under the Constitution, must exist before jurisdiction can validly be exercised. The jurisdiction of a federal court other than the High Court can be defined only with reference to the matters mentioned in ss. 75 and 76 of the Constitution — see s. 77 — and it is "quite impossible for the Parliament to give power to any judicial or other authority which goes beyond the subject matter of the legislative power conferred by the Constitution": R. v. Hickman; Ex parte Fox and Clinton [3] . Moreover, "power to determine conclusively a question upon which jurisdiction is made to depend cannot validly be conferred upon a person or body in such manner as to enable a jurisdiction to be exercised which would exceed the limits of constitutional power": R. v. Blakeley; Ex parte Association of Architects, Etc., of Australia [4] . The Family Court is a superior court of record (s. 21(2) of the Family Law Act) but the limits of its jurisdiction are defined by statute and prohibition will lie to its judges under s. 75(v) of the Constitution if the jurisdiction is exceeded. Questions of this kind have been fully discussed in relation to the former Arbitration Court in many cases, some of which are cited in R. v. Commonwealth Court of Conciliation and Arbitration; Ex parte Ozone Theatres (Aust.) Ltd. [5] , and more recently in relation to the Federal Court, in Reg. v. Federal Court of Australia; Ex parte W.A. National Football League [6] . What was said in those cases on this question is applicable to the Family Court. 1. (1945) 70 C.L.R. 598, at p. 616. 2. (1950) 82 C.L.R. 54, at p. 89. 3. (1949) 78 C.L.R. 389, at p. 399. 4. (1979) 143 C.L.R. 190, esp. at pp. 202-203, 207, 214-215, 221, 238, 240. It follows that when an application is made to the Family Court for an order for the custody of a child, and the question arises whether that child is the child of a marriage, the Family Court has the power and duty to decide whether the child is a child of the marriage. However, it cannot give itself jurisdiction by erroneously determining that question in the affirmative or deprive itself of jurisdiction by erroneously determining that question in the negative: cf. Mutual Life & Citizens' Assurance Co. Ltd. v. Attorney-General (Q.) [7] . Whether the Court has or has not jurisdiction in such a case is a question which, if jurisdiction is challenged, must ultimately be determined by the High Court. 1. (1961) 106 C.L.R. 48, at p. 56. The Supreme Court is in a somewhat similar position. Although its jurisdiction was originally virtually unlimited, there are some areas in which exclusive jurisdiction has been given to other courts, and in those areas the Supreme Court no longer has jurisdiction. One such area, as I have already said, is that occupied by "proceedings by way of a matrimonial cause" within the meaning of the Family Law Act. However, ss. 8, 39 and 40 of that Act do not (and constitutionally could not) give exclusive jurisdiction to the Family Court in proceedings which the Family Court considers, wrongly, to be by way of a matrimonial cause. It is only if the proceeding is in truth a matrimonial cause that the Supreme Court is deprived of jurisdiction. Where an application is made to the Supreme Court for the custody of a child, and a question arises whether the application is a matrimonial cause, the Supreme Court has the power and duty to decide whether the cause is a matrimonial cause. It cannot give itself jurisdiction by erroneously determining the question in the negative, or deprive itself of jurisdiction by erroneously determining the question in the affirmative. It is therefore clear that if K.J.W. is in fact a child of Mr. H., the Family Court had no jurisdiction to make an order for her custody. It is equally clear that if no proceedings had been commenced, and no order made, in the Family Court, the Supreme Court would have had jurisdiction to decide whether Mr. H. was the father, and if so to make an order for custody. What then is the position when proceedings are commenced in both the Family Court and the Supreme Court? The rule that an inferior court should not proceed to hear a case, otherwise within jurisdiction, when a superior court is exercising jurisdiction in the same matter, is of no assistance, since both the Family Court and the Supreme Court are superior courts. Until one court has made an order determining the matter, the position is clear enough. As a matter of law, each court must consider and decide the preliminary question whether it has jurisdiction. That means that in a case such as the present, each court must decide whether the child is a child of a marriage. As a matter of practice, however, it would be absurd to allow the same question to be litigated simultaneously in two different courts, and a sensible application of the principles of judicial comity should prevent such a course. The question then is whether the fact that the Family Court has made an interim order for custody has the effect of ousting the jurisdiction of the Supreme Court. Counsel who submitted that this question should be answered in the affirmative did not suggest that the matter was res judicata, or that the order gave rise to an issue estoppel. Their arguments were, first, that the proceedings in the Supreme Court were proceedings of the kind referred to in par. (f) of the definition of "matrimonial cause", and so within the exclusive jurisdiction of the Family Court, and, secondly, that the Supreme Court could not call in question the validity of the order of a federal court made in the exercise of exclusive jurisdiction. What I have already said is sufficient to dispose of the first argument. The proceedings were within par. (f) only if K.J.W. was a child of a marriage, and there is nothing in the Family Law Act that gives the Court exclusive jurisdiction to decide whether a child is a child of a marriage — that is a question on which its jurisdiction depends. And a similar answer may be made to the second argument: the order was made in the exercise of the exclusive jurisdiction of the Family Court only if the child was a child of a marriage; if that was not the case the order was beyond jurisdiction. It was submitted on behalf of the Commonwealth that the judicial power of the Commonwealth established by Ch. III of the Constitution is paramount over the judicial power of the States. With all respect, that goes too far. The decisions of this Court, which has final appellate power, of course prevail over those of all other tribunals in Australia. But the powers of other federal courts are "at once paramount and limited":Reg. v. Kirby; Ex parte Boilermakers' Society of Australia [8] . Within the limits of their jurisdiction, as defined under Ch. III, they are paramount. Beyond those limits their powers do not extend. It is not possible to find in Ch. III anything that supports the view that a judgment of a federal court given in excess of jurisdiction is binding on the courts of the States. The Constitution establishes the supremacy of federal laws, which are binding on the courts of the States (Covering cl. 5) and prevail over inconsistent State laws (s. 109). If a law of the Commonwealth, either expressly, or by implication, provides that a judgment of a federal court shall prevail over inconsistent decisions of State courts, that law will take effect accordingly and the decision of the federal court will be paramount. Such a law however would only be valid if it related to the judgments of a federal court acting within limits which were assigned to it consistently with the Constitution. 1. (1956) 94 C.L.R. 254, at p. 268. We were referred to the decisions of the United States Supreme Court, and particularly to the line of authorities of which Ableman v. Booth [9] , is one. Those cases certainly establish that in the United States if there are conflicting decisions of State and United States courts the latter prevail, but I do not understand them to go so far as to hold that a decision of a federal court, made without jurisdiction, is binding upon State courts. However, I need not explore the position in the United States, since, as has often been pointed out, the provisions relating to judicial power in the Constitution of the United States differ significantly from the Australian provisions: it is enough to mention the discussion in Collins v. Charles Marshall Pty. Ltd. [10] . We were also referred to a decision of the Supreme Court of Canada, Reg. v. The J.B. & Sons Co. Ltd. [11] , but that, too, was a case in which the federal court undoubtedly possessed jurisdiction. 1. (1858) 21 How. 506 [16 Law. Ed. 169]. 2. (1955) 92 C.L.R. 529, at pp. 544-546. 3. (1969) 9 D.L.R. (3d) 345. Nevertheless, a very real difficulty exists when the Supreme Court, in the course of exercising its power to decide the question on which its jurisdiction depends, finds that the Family Court has given a judgment which decided that question, or, as in the present case, has made an order which proceeds on an assumption of fact which is inconsistent with a finding that the Supreme Court has jurisdiction. The Supreme Court has no power to set aside the order of the Family Court — that of course can be done only by this Court or by the Family Court itself. Nor can the Supreme Court ignore the existence of the order: it may prove to be beyond jurisdiction, but the rule which allows the judgment of an inferior court to be impeached in a collateral proceeding has no application, since the Family Court is a superior court; the order will be valid and binding until it is set aside or varied: see Cameron v. Cole [12] . Although the order of the Family Court does not expressly decide the question of jurisdiction it necessarily involves a finding that jurisdiction existed. It was not a final judgment and Mr. H. was not a party to it, but until it is discharged or varied it can be effectively enforced: see ss. 64(9) and 105(1) of the Family Law Act. If would be unthinkable that the Supreme Court should make an order for the custody of a child when another order made by the Family Court remains in force in respect to the custody of the same child, with the result that two competing, and possibly conflicting, orders for custody would be in existence. The only possible courses in such a case are for the Supreme Court to refuse the application for custody, or to decline to proceed further in the exercise of its jurisdiction until the parties have had an opportunity to challenge the validity of the order of the Family Court. That might be done by an application to this Court for prohibition or by application to the Family Court itself to discharge the order. Unfortunately, a possible disadvantage of the latter course is that it has been held that the Family Court has no power to order a blood test: Lamb v. Lamb [No. 1] [13] . If that view is correct, the powers of that Court seem to be deficient. 1. (1944) 68 C.L.R. 571, at pp. 590-591, 606. 2. [1977] F.L.C. 90-225. For practical purposes it might be said that the Supreme Court has no jurisdiction to entertain the present application for custody. In principle, however, I regard it as more correct to say that the Supreme Court has jurisdiction, but that when it sees, in the exercise of its jurisdiction, that there is already an order for custody which it is bound to treat as valid, it should either dismiss the application or adjourn it to enable the order to be challenged elsewhere. What I have said relates to the application for custody. If the application for a declaration of paternity and for a direction for a blood test is made merely as ancillary to the application for custody, the Supreme Court should decline to hear that application also until the validity of the order of the Family Court is resolved. If the Supreme Court decides that the declaration of paternity and a direction for a blood test are sought for a different and independent purpose it is free to hear the application so far as it seeks that relief. If the Supreme Court did proceed to hear that part of the application, and did decide that Mr. H. is the father of the child, K.J.W., that would not in itself affect the order made by the Family Court for custody. For these reasons I would answer the question which has been asked as follows: Yes, but the Supreme Court may not grant the application for the custody of the child, or for the other orders if they are merely ancillary thereto, unless and until the order of the Family Court is set aside by the Family Court itself or by the High Court. Mason, Murphy, Wilson, Brennan and Deane JJ. The case stated asks the question: Has the Supreme Court of New South Wales jurisdiction to entertain the proceedings in that Court and to make the declarations and orders and give the directions sought in proceedings No. 4292 of 1981? In our opinion that question must be answered in the negative. The Family Court of Australia on 28 January 1981 in proceedings between the parties to the W. marriage ordered "That until further order of the Court the husband have the care and control of K.J.W. the child of the marriage on an interim basis." Although expressed to be on an interim basis, the order has not been varied or revoked. Nor has it been the subject of any appeal. There is no suggestion that it has expired in some other way. In proceedings No. 4292 of 1981 in the Supreme Court of New South Wales the plaintiffs claim, inter alia, 1. A declaration that the plaintiff R.C.H. is the father of the child K.J.W. born 4 October, 1973. 2. A direction that the defendant submit to a blood test for the purpose of ascertaining whether the defendant is the father of the said child. 3. An order that the plaintiffs have the custody of the said child K.J.W. We think it would be wrong in addressing the question which is posed in the case stated to separate the relief claimed into separate compartments and then proceed to deal with each compartment separately. We construe the application essentially as an application for custody to which the relief claimed in pars. 1 and 2 is appurtenant. So construed, the proceedings in their entirety necessarily attack both the foundation and the effect of the order of the Family Court to which we have referred. Approaching the case in this way, we see merit in disposing of the immediate problem raised by the case stated without embarking on a consideration of the important but peripheral questions which were canvassed in the course of argument. In particular, we do not find it necessary to consider the continued existence and extent of a jurisdiction in the Supreme Court to determine, in circumstances other than those which obtain in the present case, questions of paternity and custody of children who are claimed not to be the children of a marriage. The jurisdiction of the Family Court is limited, in relation to matters dealing with the custody of children, to children of a marriage. Nevertheless the grant of jurisdiction must carry with it the power to determine the existence or otherwise of facts upon which its jurisdiction depends. If the Court wrongly decides such a question then that decision will be subject to the prerogative writs or the decision will be subject to appeal. It cannot simply be ignored. So long as the order stands, the effect of the provisions of the Family Law Act 1975 Cth, as amended, conferring exclusive jurisdiction will deny the existence of jurisdiction in another Court to adjudicate on K.J.W.'s status or custody. The reason for this is that there is implicit in the order of the Family Court a finding that K.J.W. is a child of the W. marriage and a challenge to that finding would constitute a matrimonial cause within pars. (c) or (f) of the definition of that term in s. 4 of the Family Law Act: Fountain v. Alexander [14] . Under s. 8 such proceedings may be instituted only under that Act. If the Family Court on the hearing of an application to it were to find that the child is not a child of the W. marriage then it would vacate the order for custody and that would determine the proceedings in that Court. The way would then be open for any approach to the State Court for the relief required. 1. (1982) 150 C.L.R. 615. We would answer the question in the negative. Dawson J. The facts in this matter are fully set out in the judgment of the Chief Justice and I shall not repeat them. The applications in the Supreme Court for a declaration of paternity and for a direction that the defendant submit to a blood test are made pursuant to the relevant provisions of the Children (Equality of Status) Act 1976 N.S.W. which provide for application to be made to the Court by the mother or father of a child for a declaration of paternity and empower the Court to direct that a blood test be taken. The result of the test may be used in determining paternity. The application for custody appears to have been made in reliance upon s. 5 of the Infants' Custody and Settlements Act of 1899 N.S.W., sub-s. (1) of which provides: The Supreme Court may, upon the application of the mother of any minor, make such order as it may think fit regarding the custody of the minor and the right of access thereto of either parent, having regard to the welfare of the minor, and to the conduct of the parents, and to the wishes as well of the mother as of the father. An order could only be made, under this provision, if at all, upon the application of the mother, D.M.W., but it does not appear that R.C.H. seeks to invoke any other jurisdiction of the Supreme Court as to custody. It is clear, however, that the Supreme Court of New South Wales has jurisdiction to entertain the proceedings before it and to make the declaration and orders and give the directions sought unless that jurisdiction has been diminished in some relevant respect by the provisions of the Family Law Act 1975 Cth. Section 8 of the Family Law Act provides that proceedings by way of a matrimonial cause shall not be instituted except under that Act. Under s. 31 the Family Court has jurisdiction in matrimonial causes instituted or continued under the Act. Section 39(1) provides that a matrimonial cause under the Act may be instituted in the Family Court or the Supreme Court of a State or a Territory, but that section is subject to s. 40(3) under which the Governor-General may, by proclamation, fix a date as the date on and after which proceedings under the Act may not be instituted in or transferred to the Supreme Court of a State or Territory specified in the proclamation. A proclamation dated 27 May 1976 fixed 1 June 1976 as the date on and after which (subject to exceptions not presently material) matrimonial causes might not be instituted in or transferred to, amongst others, the Supreme Court of New South Wales. Section 40(4) provides that the Supreme Court of a State or Territory shall not hear and determine proceedings under the Act instituted in or transferred to that Court otherwise than in accordance with any proclamation in force under sub-s. (3). "Matrimonial cause" is defined in s. 4 of the Act to include various proceedings. Those which are relevant for the purposes of this case are: (c) proceedings between the parties to a marriage with respect to — (ii) the custody, guardianship or maintenance of, or access to, a child of the marriage; Section 4 also defines "proceedings" as meaning — a proceeding in a court, whether between parties or not, and includes cross-proceedings or an incidental proceeding in the course of or in connexion with a proceeding. Section 5 of the Family Law Act deems a child adopted since the marriage by the husband and wife or a child of the husband and wife born before the marriage to be a child of the marriage. In its original form, s. 5 also deemed a child to be a child of the marriage if it was a child of either the husband or wife (including an ex nuptial child of either of them and a child adopted by either of them) if, at the relevant time, the child was ordinarily a member of the household of the husband and wife. Apparently as a consequence of the decision in Russell v. Russell [15] the section was amended in 1976 so that a child in the last category is now deemed to be a child of the marriage only for the purposes of the application of s. 63 of that Act, a section which provides for certain declarations to be made as to the arrangements for the welfare of any children upon the pronouncement of a decree nisi. 1. (1976) 134 C.L.R. 495. The Family Court is, by s. 21(2) of the Family Law Act, declared to be a superior court of record. This legislative assertion cannot, however, be taken at face value. A superior court is a court of general jurisdiction, which is not to say that there cannot be jurisdictional limits but rather that it will be presumed to have acted within jurisdiction. This presumption is denied to inferior courts. It has been held that "nothing shall be intended to be out of the jurisdiction of a Superior Court, but that which specially appears to be so; and, on the contrary, nothing shall be intended to be within the jurisdiction of an Inferior Court but that which is so expressly alleged". See Peacock v. Bell [16] . These characteristics of a superior court are not, and for constitutional reasons cannot be, conferred upon the Family Court. A federal court created by Parliament, such as the Family Court, cannot have a general jurisdiction conferred upon it. Its jurisdiction can be no wider than that permitted by ss. 75 and 76 of the Constitution and in so far as jurisdiction is conferred, as is the case with the Family Court, in matters arising under a law or laws made by Parliament, there is a further limit to be found in the definition of Commonwealth legislative power. The limited nature of the jurisdiction which can be conferred upon federal courts created by Parliament is reflected in s. 75(v) of the Constitution which gives to this Court original jurisdiction in all matters in which a writ of mandamus or prohibition or an injunction is sought against an officer of the Commonwealth. It has long been held that officers of the Commonwealth include judicial officers and s. 33(1)(b) of the Judiciary Act 1903 Cth makes explicit what is implicit in s. 75(v) of the Constitution, namely, that this Court may make orders or direct the issue of writs requiring any court to abstain from the exercise of any federal jurisdiction which it does not possess. 1. (1667) 1 Wms. Saund. 69, at p. 74 [85 E.R. 81, at pp. 87-88]. All of this is to deny the scope to s. 21(2) of the Family Law Act which its terms would otherwise suggest. Because of the presumption as to jurisdiction, in general prohibition does not go to a superior court. See Mayor etc of London v. Cox [17] . But prohibition is the means provided to keep federal courts created by Parliament within the bounds of their jurisdictional limits and with those courts there can be no presumption as to jurisdiction to displace this remedy. Moreover, where the jurisdiction of a federal court is dependent upon the existence of facts which also mark the limit of the constitutional power to create the jurisdiction, the federal court does not have, and cannot be given, the power to determine conclusively the existence of those facts; that power is reserved to this Court. See Reg. v. Federal Court of Australia; Ex parte W.A. National Football League [18] . 1. (1867) L.R. 2 H.L. 239. 2. (1979) 143 C.L.R. 190, esp. at pp. 202-203, 213-216, 225-230. The significance of this for present purposes is that an order or judgment of the Family Court is susceptible to collateral attack for want of jurisdiction and if it be found that jurisdiction is lacking, the proceedings before that Court are corama non judice and any order or judgment is a nullity. See Parisienne Basket Shoes Pty. Ltd. v. Whyte [19] . In particular, it would be open to this Court, should the appropriate remedy be sought, to re-examine and determine for itself whether the necessary facts existed to enable the Family Court to make the order for custody in question in this case. That would mean that this Court would determine for itself, upon the material before it, which might not be the same material as was before the Family Court, whether the proceedings were "proceedings between the parties to a marriage with respect to the custody of a child of the marriage". See R. v. Blakeley [20] , R. v. Hickman [21] , and Reg. v. Federal Court of Australia; Ex parte W.A. National Football League [22] . 1. (1938) 59 C.L.R. 369. 2. (1950) 82 C.L.R. 54. 3. (1945) 70 C.L.R. 598. 4. (1979) 143 C.L.R., at pp. 203, 214-215, 228. If this Court were to determine upon examination of that question that K.J.W. was not a child of the marriage between Mr. and Mrs. W., the order for custody made by the Family Court would have been made without jurisdiction and would be a nullity. It is difficult to avoid the further conclusion that if the same question were validly to be raised in proceedings in the Supreme Court of New South Wales, that Court would also be free to determine for itself whether the facts existed upon which the jurisdiction of the Family Court depended and, if not, treat the order of the Family Court as a nullity. However, whilst the Family Law Act does not and could not give to the Family Court power conclusively to determine its own jurisdiction, it does, together with the proclamation dated 29 May 1976, preclude in the manner described above, the hearing and determination of proceedings by way of a matrimonial cause in the Supreme Court of New South Wales, putting on one side the exceptions which are not relevant for present purposes. Whether proceedings answer the description of proceedings by way of a matrimonial cause so as to fall within the jurisdiction of the Family Court and outside the jurisdiction of the other courts specified in the proclamation (see Family Law Act, ss. 8 and 40(1) and (4)) cannot be dependent upon the ultimate outcome of those proceedings. The nature of the proceedings must be characterized by the matters which fall for determination in the proceedings. In this case the relevant proceedings within the definition of "matrimonial cause" are "proceedings between the parties to a marriage with respect to the custody of a child of the marriage". In such a matrimonial cause it may be in issue whether there is a valid marriage or, if there is, whether a child is a child of the marriage but the proceedings remain a matrimonial cause whichever way those issues are decided. Notwithstanding that the issues to be determined go to jurisdiction, the Family Court does not lack power to embark upon an investigation of those issues (see Federated Engine Drivers v. Broken Hill Pty. Co. Ltd. [23] and R. v. Blakeley) even if it ultimately holds that jurisdiction is lacking. The proceedings in which it determines those issues may nonetheless constitute a matrimonial cause. This would, I think, be the proper conclusion without recourse to the definition of proceedings in s. 4 of the Family Law Act, but that definition, which includes within the term "proceedings" an "incidental proceeding in the course of or in connexion with a proceeding" makes it clear in my view that an inquiry by the Family Court into the facts necessary to found its own jurisdiction itself falls within the definition of a matrimonial cause. 1. (1911) 12 C.L.R. 398. Necessarily proceedings which answer the description of a matrimonial cause under the Family Law Act will, if they can be brought at all, be instituted under that Act. See s. 8(1). But proceedings under that Act may not be heard and determined by the Supreme Court of a State or Territory where the institution of such proceedings in such a court is prohibited by proclamation (s. 40(3) and (4)). Such is the case with the Supreme Court of New South Wales. The question is therefore raised whether the proceedings in this case in that Court fall within the definition of a matrimonial cause and, in particular, whether they are "proceedings between the parties to a marriage with respect to the custody of a child of the marriage", including an "incidental proceeding in the course of or in connexion with" those proceedings. In so far as the claim for custody which has been instituted in the Supreme Court involves the determination of the same matters which would fall for the determination of the Family Court were proceedings for custody to be instituted in that Court, those proceedings in my view answer the description of a matrimonial cause under the Family Law Act and may not be heard or determined by that Court. And it is precisely those matters which the Supreme Court must decide upon the issues raised in the claim for custody before it which answer the description of a matrimonial cause in the Family Law Act and would be required to be determined by the Family Court if proceedings for custody were to be instituted in that Court. That is to say, the Supreme Court, if it were to proceed, would be required to determine whether the proceedings before it were proceedings between the parties to a marriage with respect to the custody of a child of a marriage in order to determine whether its jurisdiction was established. The hearing and determination of those matters involves the hearing and determination of proceedings under the Family Law Act which may only be instituted under that Act (see s. 8(1)) and may not, by reason of the proclamation and s. 40(4) of that Act, take place in the Supreme Court of New South Wales. The claims in the Supreme Court for a declaration of paternity and for a direction that the defendant submit to a blood test may, I think, be regarded separately from the claim for custody. Paternity is a fact which is relevant to matters other than custody, for example, succession. Perhaps the declaration and direction are sought in this case with a view to their being of assistance in the application for an order for custody of the child, but to conclude that this is so or that this is the sole reason for seeking this relief would be to make an assumption which I am not prepared to make. If the declaration and direction were sought in separate proceedings, there could be no question of the jurisdiction of the Supreme Court over such matters and it does not seem to me, without more, to make any difference to that jurisdiction that the orders are sought in the same proceedings as an order for custody. I would answer the question as follows: The Supreme Court of New South Wales does not have jurisdiction to hear and determine the application for an order that the plaintiffs have the custody of the child, K.J.W. Otherwise that Court has jurisdiction to entertain the proceedings in that Court and to make the declarations and orders and give the directions sought in proceedings No. 4292 of 1981.