The case of State of Missouri v. Holland established that a state can't prevent the enforcement of federal regulations related to the protection of migratory birds. The Treaty of August 16, 1916, with Great Britain, which provides for the protection of migratory birds in the United States and Canada, is within the treaty-making power conferred by Art. II, § 2, of the Constitution. The Act of July 3, 1918, which prohibits the killing, capturing, or selling of migratory birds, is valid under Art. I, § 8, of the Constitution, as a necessary and proper means of effectuating the treaty. The court found that the federal government has the power to regulate migratory birds, and the states cannot interfere with this power. The State of Missouri filed a bill to prevent the enforcement of the Migratory Bird Treaty Act, claiming it violates the Tenth Amendment and infringes on the state's sovereign rights. The District Court dismissed the case, but the State appealed.

Referring to the Tenth Amendment is not enough to determine if the Migratory Bird Treaty Act violates states' rights. Treaties made under the authority of the United States are declared the supreme law of the land. The validity of the treaty and statute must be determined separately. While there may be limitations to the treaty-making power, they must be determined differently. The treaty in question does not violate any prohibitory words in the Constitution, and we must consider what the country has become in interpreting the Tenth Amendment.

The State's claim of exclusive authority over migratory birds is weak as wild birds are not possessed by anyone. The treaty deals with creatures within state borders that must be carried out by officers of the United States within the same territory. Valid treaties may override state power, and a national interest of great importance is at stake. The reliance on states is insufficient, and the United States is not forbidden to act. The treaty and statute must be upheld. The decision is affirmed, with two justices dissenting.