Final answer:
The subject of this question is Social Studies. The Tenth Amendment of the United States Constitution affirms the states' reserved powers.
Step-by-step explanation:
The subject of this question is Social Studies. The phrase in question is a part of the Tenth Amendment of the United States Constitution. The Tenth Amendment affirms the states' reserved powers and states that any powers not delegated to the United States by the Constitution or prohibited by the Constitution to the states are reserved to the states respectively or to the people.