Can the DOD declare that airspace off limits to civil aircraft?

The Department of Defense (DOD) wishes to dedicate a sizeable block of airspace over North Dakota to the exclusive use of military unmanned aircraft systems. Can the DOD declare that airspace off limits to civil aircraft? How can the DOD accomplish that objective? Will interested persons and organizations, such as the Aircraft Owners and Pilots Association, have an opportunity to express their opinions about the proposed change? If so, how?