Federal Law "Controlling" over a Treaty

As declared by the Court in Whitney v. Robertson, 124 U.S. 190 (1888):

"... if there be any conflict between the stipulations of the treaty and the requirements of the law, the latter must control. A treaty is primarily a contract between two or more independent nations, and is so regarded by writers on public law. For the infraction of its provisions a remedy must be sought by the injured party through reclamations upon the other. When the stipulations are not self-executing, they can only be enforced pursuant to legislation to carry them into effect, and such legislation is as much subject to modification and repeal by congress as legislation upon any other subject. If the treaty contains stipulations which are self-executing, that is, require no legislation to make them operative, to that extent they have the force and effect of a legislative enactment. Congress may modify such provisions, so far as they bind the United States, or supersede them altogether. By the constitution, a treaty is placed on the same footing, and made of like obligation, with an act of legislation. Both are declared by that instrument to be the supreme law of the land, and no superior efficacy is given to either over the other. When the two relate to the same subject, the courts will always endeavor to construe them so as to give effect to both, if that can be done without violating the language of either; but, if the two are inconsistent, the one last in date will control the other: provided, always, the stipulation of the treaty on the subject is self-executing. If the country with which the treaty is made is dissatisfied with the action of the legislative department, it may present its complaint to the executive head of the government, and take such other measures as it may deem essential for the protection of its interests. The courts can afford no redress. Whether the complaining nation has just cause of complaint, or our country was justified in its legislation, are not matters for judicial cognizance. In Taylor v. Morton, 2 Curt. 454, 459, this subject was very elaborately considered at the circuit by Mr. Justice CURTIS, of this court, and he held that whether a treaty with a foreign sovereign had been violated;  whether the consideration of a particular stipulation of the treaty had been voluntarily withdrawn by one party, so that it was no longer obligatory on the other; whether the views and acts of a foreign sovereign had given just occasion to the legislative department of our government to withhold the execution of a promise contained in a treaty, or to act in direct contravention of such promise,- were not judicial questions; that the power to determine these matters had not been confided to the judiciary, which has no suitable means to exercise it, but to the executive and legislative departments of our government; and that they belong to diplomacy and legislation, and not to the administration of the laws. And he justly observed, as a necessary consequence of these views, that, if the power to determine these matters is vested in congress, it is wholly immaterial to inquire whether by the act assailed it has departed from the treaty or not, or whether such departure was by accident or design, and, if the latter, whether the reasons were good or bad.

"In these views we fully concur. It follows, therefore, that, when a law is clear in its provisions, its validity cannot be assailed before the courts for want of conformity to stipulations of a previous treaty not already executed. Considerations of that character belong to another department of the government. The duty of the courts is to construe and give effect to the latest expression of the sovereign will. In Head-Money Cases, 112 U.S. 580, 5 Sup. Ct. Rep. 247, it was objected to an act of congress that it violated provisions contained in treaties with foreign nations, but the court replied that, so far as the provisions of the act were in conflict with any treaty, they must prevail in all the courts of the country; and, after a full and elaborate consideration of the subject, it held that, 'so far as a treaty made by the United States with any foreign nation can be the subject of judicial cognizance in the courts of this country, it is subject to such acts as congress may pass for its enforcement, modification, or repeal.'