Joint Jurisdiction. Courts-martial have exclusive jurisdiction over purely military offenses. In the case of an offense that violates the Uniform Code of Military Justice and the criminal law of a State, other Federal law, or all three, it must be determined which jurisdiction will prosecute. This decision is normally made through coordination between appropriate military authorities (ordinarily the chief military lawyer at an installation (Staff Judge Advocate)) and appropriate civilian authorities (United States Attorney or District Attorney’s Office).
The fact that an accused is subject to trial by court-martial does not eliminate the possibility of trial by another jurisdiction, either in addition to or in lieu of court-martial. Under the United States Constitution, a person may not be tried for the same misconduct by both a court-martial and another federal court. Such an act would violate the Constitution’s double jeopardy clause.
Criminal prosecution in both federal and state courts is also a constitutional possibility. The Constitution’s double jeopardy clause is not applicable because two different sovereigns are involved, i.e. the federal government and state government. As a matter of policy, however, a person who is pending trial or has been tried by a State court is ordinarily not tried by court-martial for the same act.