martial law

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Temporary rule by military authorities, imposed on a civilian population especially in time of war or when civil authority has broken down.
• noun The law imposed on an occupied territory by occupying military forces.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun Rules by military authorities, especially when imposed on a civilian population in time of war or other crisis, or in an occupied territory

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun the body of law imposed by the military over civilian affairs (usually in time of war or civil crisis); overrides civil law