The sources of state power are specifically outlined in

The sources of state power are specifically outlined in the Tenth Amendment of the Bill of Rights.
When the Constitution was first proposed, many people were concerned about the federal government become too powerful. A group known as the anti-federalists pushed for a way to legally set aside certain rights and powers to individual states.

This amendment was added to satisfy the anti-federalists who were concerned that the Constitution would grant the federal government unlimited power.

The Tenth Amendment states that all powers that are not specifically given to the federal government are reserved to individual states.