The Tenth Amendment to the Constitution states that "The powers not delegated to the United States by the Constitution, nor prohibited by it to the states, are reserved to the states or to the people." This amendment is a source of law that limits the powers of the federal government and reserves certain powers to the states or the people. It is a principle of federalism, which divides the power between the federal government and the state governments. The powers that are not delegated to the federal government are left to the states or the people to decide.