When exercising jurisdiction determined by the nature of the subjects litigated, which subjects have been placed by the Constitution within the legislative control of Congress, the federal courts, of course, administer the federal statutes and the Constitution so far as it is self-executory. In one case at least, in maritime and admiralty matters, the grant by the Constitution of judicial power has been construed to carry with it a grant of legislative power to provide the law to be applied.1 Where the federal courts obtain jurisdiction wholly because of the character of the parties, the federal courts, generally speaking, apply the state or other law which would apply were the suits brought in the state courts. The exceptions to this rule have in a measure been already considered in connection with the impairment of the obligation of contracts, and will be further considered in the next following section. In the present section will be considered the force and applicability of principles of international law in the federal courts.
In so far as applicable, American courts apply established doctrines of international law. Not, however, in the sense that they apply a body of law which has not been derived from and based upon the sovereign will of the American State, but upon the theory that this body of rules is first impliedly adopted by the State and thus made a portion of its own municipal law. Resting thus upon the implied assent and adoption of the United States, these principles of international law are subject to express modification by statute. In the very early case of The Charming Betsy,2 decided in 1804, it seems to have been accepted as a principle not needing argument that the court would be bound by an act of Congress providing a rule different from that laid down by international law, the only observation made being that "an act of Congress ought never to be construed to violate the law of nations if any other possible construction remains." In The Nereide3 Marshall again declares: "Till an act [of Congress] be passed, the court is bound by the law of nations, which is a part of the law of the land."
1 See Section 646.
In Hilton v. Guyot4 the court say: "International law in its widest and most comprehensive sense - including not only questions of right between nations, governed by what has been appropriately called the law of nations, but also questions arising under what is usually called private international law, or the conflict of laws, and concerning the rights of persons within the territory and dominion of one nation, by reason of acts, private or public, done within the dominion of another nation - is part of our law, and must be ascertained and administered by the courts of justice, as often as such questions are presented in litigation between man and man, duly submitted to their determination.
"The most certain guide no doubt for the decisions of such questions is a treaty or a statute of this country. But when, as is the case here, there is no written law upon the subject, the duty still rests upon the judicial tribunals of ascertaining and declaring what the law is whenever it becomes necessary to do so in order to determine the rights of parties to suits regularly brought before them. In doing this, the courts must obtain such aid as they can from judicial decisions, from the works of jurists and commentators, and from the acts and usages of civilized nations." 5
2 2 Cr. 64; 2 L. ed. 208.
3 9 Cr. 3S8; 3 L. ed. 769.
4 159 U. S. 113; 16 Sup. Ct. Rep. 139; 40 L. ed. 95.
5 Citing Fremont v. United States, 17 How. 542; 15 L. ed. 241: Sears v. The Scotia, 14 Wall. 170; 20 L. ed. 822; Respublica v. De Longchamps, 1 Dall. III; 1 L. ed. 59; Moultrie v. Hunt, 23 N. Y. 394, 396.
In the case of The Lottawanna, sub nomine Rodd v. Heart,6 is set out in the clearest possible manner the extent to which, and the manner in which, any body of law not originally municipal, may, by adoption, become such. That case had reference to the adoption by the United States of the general principles of maritime law, but, as is pointed out in the argument, the principle is the same with reference to international law. Justice Bradley, speaking for the court, said:
"The ground on which we are asked to overrule the judgment in the case of The General Smith is, that by the general maritime law, those who furnish necessary materials, repairs and supplies to a vessel, have a lien on such a vessel therefor, as well when furnished in her home port as when furnished in a foreign port, and that the courts of admiralty are bound to give effect to that lien.
"The proposition affirms that the general maritime law governs this case, and is binding on the courts of the United States.
"But it is hardly necessary to argue that the general maritime law is only so far operative as law in any country as it is adopted by the laws and usages of that country. In this respect it is like international law or the laws of war, which have the effect of law in no country further than they are accepted and received as such; or, like the case of the civil law, which forms the basis of most European laws, but which has the force of law in each State only so far as it is adopted therein, and with such modifications as are deemed expedient. The adoption of the common law by the several States of this Union also presents an analogous case. It is the basis of all the State laws; but is modified as each sees fit. Perhaps the maritime law is more uniformly followed by commercial nations than the civil and common law by those who use them. But, like those laws, however fixed, definite and beneficial the theoretical code of maritime law may be, it can have only so far the effect of law in any country as it is permitted to have. But the actual maritime law can hardly be said to have a fixed and definite form as to all the subjects which may be embraced within its scope. Whilst it is true that the great mass of maritime law is the same in all commercial countries, yet in each country peculiarities exist either as to some of the rules, or in the mode of enforcing them. Especially is this the case on the outside boundaries of the law, where it comes in contact with or shades off into the local or municipal law of the particular country and affects only its own merchants or people in their relations to each other. Whereas, in matters affecting the stranger or foreigner, the commonly-received law of the whole commercial world is more assiduously observed - as, in justice, it should be. No one doubts that every nation may adopt its own maritime code. France may adopt one; England another; the United States a third; still the convenience of the commercial world, bound together, as it is, by mutual relations of trade and intercourse, demands that in all esssential things wherein those relations bring them in contact, there should be a uniform law founded on natural reason and justice. Hence the adoption by all commercial nations (our own included) of the general maritime law as the basis and groundwork of all their maritime regulations. But no nation regards itself as precluded from making occasional modifications suited to its locality and the genius of its own people and institutions, especially in matters that are of merely local and municipal consequence, and do not affect other nations. It will be found, therefore, that the maritime Codes of France, England, Sweden, and other countries, are not one and the same in every particular; but that, whilst there is a general correspondence between them, arising from the fact that each adopts the general principles, and the great mass of the general maritime law as the basis of its system, there are varying shades of difference corresponding to the respective territories, climate and genius of the people of each country respectively. Each State adopts the maritime law, not as a code having any independent or inherent force, proprio vigore, but as its own law, with such modifications and qualifications as it sees fit. Thus adopted and thus qualified in each case, it becomes the maritime law of the particular nation which adopts it. And without such voluntary adoption it would not be law. And thus it happens, that, from the general practice of commercial nations in making the same general law the basis and groundwork of their respective maritime systems, the great mass of maritime law which is thus received by these nations in common, comes to be the common maritime law of the world."
6 21 Wall. 558; 22 L. ed. 654.