Final answer:
The Tenth Amendment gives states their powers by reserving all powers not explicitly delegated to the federal government, or prohibited to the states, to the states or the people.
Step-by-step explanation:
States gain much of their power from the Tenth Amendment. The Tenth Amendment of the United States Constitution reserves all powers not explicitly delegated to the federal government, or prohibited to the states, to the states themselves or to the people. This is often interpreted as the constitutional foundation for states' rights, ensuring that the federal government does not overstep its intended bounds. The Tenth Amendment underscores the federal system in the United States, where both the states and the federal government have spheres of influence, and it is an important part of the balance of power between the two levels of government.