Final answer:
The Supremacy Clause is the provision in Article VI of the U.S. Constitution that establishes federal laws and the Constitution itself as the supreme law of the land, overriding conflicting state laws when enacted under constitutional authority.
Step-by-step explanation:
When conflict arises between federal and state laws, the Supremacy Clause states that the U.S. Constitution, as well as laws and treaties created in accordance with the U.S. Constitution, supersede state and local laws. This clause, contained in Article VI of the Constitution, asserts that federal laws have precedence over state laws when there is a direct conflict, provided that those federal laws are made under the authority of the Constitution. Notably, this governance principle was affirmed in the landmark Supreme Court case of McCulloch v. Maryland in 1819, illustrating the precedence of federal legislation and constitutional provisions over state statutes.
The Supremacy Clause serves as a cornerstone for maintaining legal uniformity across the United States, ensuring that the federal government and its laws remain 'supreme within its sphere of action,' as declared by the Supreme Court. The application of this clause ensures a cohesive legal framework for the country, even in complex cases like the regulation of marijuana, where federal and state laws may diverge significantly.