In support of the first contention it was argued that as, by the Constitution, the power of the Commonwealth Parliament is expressed to be "to make laws for the peace, order, and good government of the Commonwealth" with respect to the enumerated topics, a Commonwealth Act would not be valid if it provided for matters with which the Commonwealth could have no concern. By way of emphatic illustration of this argument extravagant hypotheses were suggested, such as Australian legislation dealing with marriages of foreign people in foreign lands, or with pensions, or weights and measures in foreign places, and so forth. But any Commonwealth statute if it be a law in respect of one of the subjects mentioned in s. 51 is constitutionally valid. If it purported to affect the internal affairs of another country it might be unenforceable, ineffectual and contrary to the comity of nations. It would be ultra vires, in the sense in which Dicey used the expression for the purposes of private international law (Conflict of Laws 5th ed. (1932) 20). But it would not be ultra vires the Commonwealth Parliament in a constitutional sense. A statute in general terms is always construed as prima facie affecting things and persons within the territory of the country which enacts it, and as not affecting things elsewhere. Even where some extra-territorial application is clearly intended, this application will often be restricted to persons and things with which the country of the legislature has some direct relation or concern, for example, its nationals and their property. This is simply a rule of construction, the corollary of the principle that sovereignty is, by the law of all countries that have inherited the common law, regarded as territorial; because territorial boundaries ordinarily mark the limits of the effective enforcement of municipal law. Territoriality (as an element in domicile, residence or presence) rather than political allegiance has by our law been recognized as the ordinary foundation of curial jurisdiction. But legislative competence is different. If the Commonwealth Parliament were to legislate gratuitously in respect of foreign persons in foreign territory, in one of the ways fancifully suggested in argument, an Australian court could not hold the legislation was invalid - provided, always, that it was in respect of one of the matters in s. 51. Vis-à-vis the States, the competence of the Commonwealth Parliament remains limited and the Statute of Westminster does not affect this. But in respect of the matters set out in s. 51 the Parliament is now in reality fully sovereign, except perhaps in a theoretical unrealistic sense satisfying to convinced Austinians who see the Statute of Westminster as a repealable enactment of the Imperial Parliament. Whatever limitations international comity may impose are the consequences of considerations of political propriety and of the limitations of political power, not of legal capacity. The Privy Council summed the whole matter up: "Their Lordships would point out that what is here in issue is the extent of the legislative power of a Dominion legislature having regard to the language of the Statute of Westminster. This is not the same question as the question whether legislative power is so used as to extend beyond what will prove to be effective. A legislature which passes a law having extra-territorial operation may find that what it has enacted cannot be directly enforced, but the Act is not invalid on that account, and the courts of its country must enforce the law with the machinery available to them" (British Columbia Electric Railway Co., Ltd. v. The King [1] . Where the Statute of Westminster does not apply - for example, in relation to enactments of a State legislature (especially fiscal legislation) affecting things outside the territory of the legislature - words such as "peace, order, and good government" in a constitutional instrument may still be of cardinal importance. But this is only because they have become the accepted touchstone of whatever territorial limitations still exist upon the powers of subordinate legislatures in British dependencies (see Johnson v. Commissioner of Stamp Duties [2] and cases there referred to). That the requirements of peace, order, and good government provide the only limitation of the validity of any extra-territorial legislation otherwise within power has been accepted by this Court since Croft v. Dunphy [3] (e.g. Trustees Executors and Agency Co. Ltd. v. Federal Commissioner of Taxation [4] , per Evatt J. [5] ; Crowe v. The Commonwealth [6] , per Starke J. [7] ). The words "peace, order, and good government" or the similar expression "peace, welfare, and good government" are, it has now been said, words of very wide import giving a wide discretion to any legislature empowered to pass laws for such purposes (Attorney-General for Saskatchewan v. Canadian Pacific Railway Co. [8] ). Their significance in relation to territorial limitations upon colonial legislatures was foreshadowed in Ashbury v. Ellis [9] and the view which now prevails of their effect in this context is, in substance, that which Sir John Salmond put forward [10] . He urged it upon the Supreme Court of New Zealand in R. v. Lander [1] ; but it then gained the assent only of Stout C.J. But although the requirements of "peace, order and good government", rather than any purely geographical consideration, are now the measure of the territorial limitation upon legislative competence, where that limitation still applies, it is, I think, a mistake to regard the phrase as the origin of the prohibition of extra-territorial legislation by colonial legislatures. Indeed the origin and extent of that much discussed doctrine are obscure. Professor W. Harrison Moore said of the words "peace, order, and good government" in s. 51 of the Commonwealth Constitution: "They do not in themselves confer any substantive power, nor do they, it is submitted, warrant the view that the matters enumerated are merely means towards an end. They simply express the fact that in "a general and remote sense the purpose and design of every law is to promote the welfare of the community"." (Commonwealth of Australia 2nd ed. (1910) pp. 274, 275). They or similar phrases such as "peace, welfare and good government" have long been a common form in instruments conferring legislative power in British dependencies. A list of statutes in which they appear going back to 1774 (14 Geo. III c. 83) appears in Quick & Garran on The Constitution (1901) p. 511. But they were in use before 1774. In Stokes Constitution of the British Colonies in America, published in 1783, the common form of a colonial governor's commission in the American colonies before the Declaration of Independence is set out. It contains the following: "And you the said A. B. by and with the consent of our said Council and Assembly, or the major part of them respectively, shall have full power and authority to make constitute and ordain laws, statutes and ordinances for the public peace, welfare and good government of our said Province, and of the people and inhabitants thereof, and such others as shall resort thereto and for the benefit of us our heirs and successors; which said laws statutes and ordinances are not to be repugnant, but as near as may be agreeable to the law and statutes of this our Kingdom of Great Britain". I do not know when this form was first used; but it very closely follows the words of the commission which Charles II issued to Sir Jonathan Atkins as Governor of Barbados in 1673 (see Labaree, Royal Instructions to Colonial Governors ). So far as the Commonwealth is concerned, it is now for Parliament alone to judge whether a measure in respect of any topic on which it has power to legislate is in fact for the peace order and good government of the Commonwealth (cf. Riel v. The Queen [2] ).