The Law of Nations and Municipal Law differ, secondly, regarding the relations they regulate. Municipal Law regulates relations between the individuals under the sway of the respective State and the relations between this State and the respective individuals. International Law, on the other hand, regulates relations between the member States of the Family of Nations.
The Law of Nations and Municipal Law differ, thirdly, with regard to the substance of their law: whereas Municipal Law is a law of a Sovereign over individuals subjected to his sway, the Law of Nations is a law not above, but between Sovereign States, and therefore a weaker law.[21]
[Sidenote: Law of Nations never _per se_ Municipal Law.]
§ 21. If the Law of Nations and Municipal Law differ as demonstrated, the Law of Nations can neither as a body nor in parts be _per se_ a part of Municipal Law. Just as Municipal Law lacks the power of altering or creating rules of International Law, so the latter lacks absolutely the power of altering or creating rules of Municipal Law. If, according to the Municipal Law of an individual State, the Law of Nations as a body or in parts is considered the law of the land, this can only be so either by municipal custom or by statute, and then the respective rules of the Law of Nations have by adoption[22] become at the same time rules of Municipal Law. Wherever and whenever such total or partial adoption has not taken place, municipal courts cannot be considered to be bound by International Law, because it has, _per se_, no power over municipal courts.[23] And if it happens that a rule of Municipal Law is in indubitable conflict with a rule of the Law of Nations, municipal courts must apply the former. If, on the other hand, a rule of the Law of Nations regulates a fact without conflicting with, but without expressly or tacitly having been adopted by Municipal Law, municipal courts cannot apply such rule of the Law of Nations.
[Footnote 22: This has been done by the United States. See The Nereide, 9 Cranch, 388; United States _v._ Smith, 5 Wheaton, 153; The Scotia, 14 Wallace, 170; The Paquette Habana, 175 United States, 677. See also Taylor, § 103, and Scott in A.J. I. (1908), pp. 852-865. As regards Great Britain, see Blackstone, IV. ch. 5, and Westlake in _The Law Quarterly Review_, XXII. (1906), pp. 14-26; see also the case of the West Rand Central Mining Co. _v._ The King (1905), 2 K. B. 391.]