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.