Final answer:
The concept that refers to powers not granted to the federal government being reserved for the states is federalism. It is an essential principle in the U.S. Constitution that ensures a balance between national authority and state sovereignty.
Step-by-step explanation:
The concept that describes a government structure where powers not explicitly granted to the federal government are delegated to state governments is federalism. Under this system, the federal government has certain enumerated powers, whereas the powers not specifically mentioned remain with the states. This is outlined in the Tenth Amendment to the U.S. Constitution. Federalism allows for a division of power, where the federal government handles national and international issues, and the states address the more localized concerns of their citizens. This balance aims to prevent an overconcentration of power in a single authority, promoting instead a system where different levels of government have sovereignty over different areas.