Supremacy Clause: Part of Article VI, Section 2 of the U.S Constitution stating that all treaties and federal laws are 'the supreme Law of the Land.'
Preemption Doctrine: A doctrine based on Supremacy Clause which holds that certain matters are primarily if not exclusively within federal control.
Commerce Clause: The clause in Article I, Section 8 giving Congress exclusive power over trade activities among states and with foreign nations and Indian tribes.