Article VI, clause 2 of the United States Constitution, known as the supremacy clause establishes US Federal Law as the controlling or supreme law in the United States. As a result not only does Federal Law over-rule contradictory state laws (with very rare exceptions, if the Federal Government lack proper jurisdiction), but where the US has established what is described as a comprehensive statutory framework, it is considered to have “preempted” that subject area precluding a competing state law scheme.

Preemption applies to US copyright law (17 U.S.C. 101) and patent law but not to trademark law (15 U.S.C. § 1125) or antitrust law (except where the state law would has irreconcilable differences with US antitrust law, e.g., it would authorize otherwise illegal conduct.) However, in general preemption does not apply to transactions in IP rights – i.e., sales and transfers – where the law of the contract governs, including state contract and property law principles.