How do the Tenth Amendment and reserved powers limit the national government?

The Tenth Amendment serves as a foundational principle of American federalism by clarifying that the national government possesses only those powers specifically delegated to it by the Constitution. All other powers—often referred to as residual or reserved powers—remain with the states or the people.12

Rather than granting states new authority, the amendment functions as a structural reminder that federal power is limited to its enumerated scope. By reserving non-delegated powers to the states, it establishes a constitutional boundary that prevents the federal government from exercising authority over matters not explicitly or implicitly granted to it.12

While the Supreme Court has historically balanced this against the federal government's implied powers—such as those derived from the "necessary and proper" clause—the Tenth Amendment remains a vital legal and political tool. It ensures that states retain the autonomy to establish their own laws and policies, provided those actions do not conflict with the supremacy of the national government or the Constitution itself.12