02-18-2012, 11:27 PM
http://uscode.house.gov/download/pls/04C1.txt
5. The heads of the several departments and agencies of the
Government may direct that the flag of the United States be flown
at half-staff on buildings, grounds, or naval vessels under their
jurisdiction on occasions other than those specified herein which
they consider proper, and that suitable military honors be rendered
as appropriate.