Strictly speaking, there can be no devolution of powers from the U.S. federal government to the states without constitutional change because the federal government possesses only those powers delegated to it by the people of the states through the U.S. Constitution. All other powers are reserved to the states or to the people (see the Tenth Amendment to the U.S. Constitution). Hence, the states are sovereign in their own right, and they derive their self-governing powers from their own people, not from the U.S. government or the people of the United States. However, each U.S. state government is a unitary government possessing inherent and plenary residual powers, whereas in the case of local governments there is no inherent or sovereign right of self-government. Consequently, it is possible to devolve powers from a state government to local governments.
https://encyclopedia.federalism.org/index.php/Devolution