Mr. Justice HOLMES delivered the opinion of the Court.

This is a bill in equity brought by the State of Missouri to prevent a game warden of the United States from attempting to enforce the Migratory Bird Treaty Act of July 3, 1918, c. 128, 40 Stat. 755, and the regulations made by the Secretary of Agriculture in pursuance of the same. The ground of the bill is that the statute is an unconstitutional interference with the rights reserved to the States by the Tenth Amendment...

It is said that a treaty cannot be valid if it infringes the Constitution, that there are limits, therefore, to the treaty-making power, and that one such limit is that what an act of Congress could not do unaided, in derogation of the powers reserved to the States, a treaty cannot do. An earlier act of Congress that attempted by itself and not in pursuance of a treaty to regulate the killing of migratory birds within the States had been held bad in the District Court.... Those decisions were supported by arguments that migratory birds were owned by the States in their sovereign capacity for the benefit of their people, and that ... this control was one that Congress had no power to displace. The same argument is supposed to apply now with equal force.

Whether the two cases cited were decided rightly or not they cannot be accepted as a test of the treaty power. Acts of Congress are the supreme law of the land only when made in pursuance of the Constitution, while treaties are declared to be so when made under the authority of the United States. It is open to question whether the authority of the United States means more than the formal acts prescribed to make the convention. We do not mean to imply that there are no qualifications to the treaty-making power; but they must be ascertained in a different way. It is obvious that there may be matters of the sharpest exigency for the national well being that an act of Congress could not deal with but that a treaty followed by such an act could, and it is not lightly to be assumed that, in matters requiring national action, 'a power which must belong to and somewhere reside in every civilized government' is not to be found.... We are not yet discussing the particular case before us but only are considering the validity of the test proposed. With regard to that we may add that when we are dealing with words that also are a constituent act, like the Constitution of the United States, we must realize that they have called into life a being the development of which could not have been foreseen completely by the most gifted of its begetters. It was enough for them to realize or to hope that they had created an organism; it has taken a century and has cost their successors much sweat and blood to prove that they created a nation. The case before us must be considered in the light of our whole experience and not merely in that of what was said a hundred years ago. The treaty in question does not contravene any prohibitory words to be found in the Constitution. The only question is whether it is forbidden by some invisible radiation from the general terms of the Tenth Amendment. We must consider what this country has become in deciding what that amendment has reserved.