What is "reserved powers"

n. (context US English) Powers reserved for the states under the 10th Amendment of the United States Constitution.

In comparative federalism and comparative constitutionalism, reserved powers or residual powers are those powers which are not "enumerated" (written down, assigned). In various federal and decentralized political systems, certain subjects are assigned to either the central (or federal) government or the regional (or state or provincial) government; however it is not possible to list all possible subjects that might be legislated on for all time. Therefore, the framers of major constitutional documents tend to assign all other subjects that may arise after the document is enacted to one of the two orders of government. This is considered a major power in its own right.

Reserved powers are distinguished from concurrent powers (which are shared by the federal and constituent governments). Reserved powers are also distinguished from exclusively delegated powers, such as the exclusive federal powers in the United States.