“Federal preemption” refers to a legal doctrine in U.S. law whereby federal law supersedes state or local laws when there is a conflict. This principle arises from the Supremacy Clause of the U.S. Constitution, which states that federal laws take precedence over state laws. Preemption can be either express, where Congress explicitly states its intent, or implied, where the federal regulatory scheme is so comprehensive that it leaves no room for state action. This concept is crucial in determining the balance of power between different levels of government and impacts areas such as environmental policy, civil rights, and healthcare.