Rights reserved to states or people – 1791
“The powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved to the States respectively, or to the people.”
The 10th amendment was put in place to further define the balance of powers between the states and the federal government.
If the constitution does expressly delegate a power to the United States or prohibit it to the states then it belongs to the states and/or respectively to the people.
See: Previous Amendment (Ninth Amendment) – Next Amendment (Eleventh Amendment)