The Supremacy Clause of the US Constitution, contained in Article VI. Article VI All debts contracted and engagements entered into, before the adoption of this Constitution, shall be as valid against the United States under this Constitution, as under the Confederation. This Constitution, and the laws of the United States which shall be made in pursuance thereof; and all treaties made, or which shall be made, under the authority of the United States, shall be the supreme law of the land; and the judges in every state shall be bound thereby, anything in the Constitution or laws of any State to the contrary notwithstanding. The Senators and Representatives before mentioned, and the members of the several state legislatures, and all executive and judicial officers, both of the United States and of the several states, shall be bound by oath or affirmation, to support this Constitution; but no religious test shall ever be required as a qualification to any office or public trust under the United States.
Article V of the U.S. Constitution provides that when the National government attempts to enact uniform laws across its territories, it is to grant a power to each particular state government to pass laws in conformity, to “promulgate such uniform laws upon the subjects of a [State]…[to the end] that the law thereof may be uniform, and there be no diversity of laws upon the subject of the same.” No, this means that once a law is enacted by a legislature in a state, it gets enforced at the national level as the law in a federal country, if there was such a uniform law (it should be noted that there have been some issues with this, as there was in the early days of the United States, particularly in the Northwest Territories). If the federal government attempted to enact uniform laws across its territory, it would be unlawful.