Which amendment grants states the power to regulate their own affairs?

The Tenth Amendment is the reason states have the power to regulate their own affairs because it explicitly reserves powers not delegated to the federal government to the states and the people. This amendment is a key part of the Bill of Rights and emphasizes the principle of federalism, which maintains a clear distinction between state and federal powers. By establishing that any powers that are not granted to the federal government are reserved for the states, the Tenth Amendment supports the autonomy of state governments to make decisions on matters such as education, law enforcement, and local governance. This is foundational for understanding the balance of power in the U.S. political system and highlights the rights of states in managing their own legislative processes without unwarranted federal interference.