Excuse my ignorance, but how does a DoD Directive signed by the Deputy Secretary of Defense constitute "law"? My understanding of law is that is created by the legislative branch, approved by the executive branch and ruled constitutional/unconstitutional by the judicial branch.
DoD Directives are broad DoD policy documents containing what is required by legislation, the President, or the Secretary of Defense to initiate, govern, or regulate actions or conduct by the DoD Components within their specific areas of responsibilities. DoD Directives establish or describe policy, programs, and organizations; define missions; provide authority; and assign responsibilities.
The military operates by different rules than civilians (they have to keep order within the ranks). And, the Civil Service workers within the military, and the troops have to follow federal government guidelines which prohibit politicking on ANY level (Federal, State, and Local), except for casting a ballot.