Courts-martial have sole jurisdiction over wholly military offenses. In the case of an offense that violates the Uniform Code of Military Justice (UCMJ) and the criminal law of a State, other Federal law, (or all three) it must be determined which jurisdiction will move forward with the prosecution. This decision is made through coordination between the appropriate military authorities (ordinarily the Staff Judge Advocate) and appropriate civilian authorities, such as the United States Attorney or District Attorney’s Office.
Being subject to a court-martial does not eliminate the possibility of trial by another jurisdiction, either in lieu of or in addition to a court-martial. Under the U.S. Constitution, a service member cannot be tried for the same misconduct by both a court-martial and another federal court. Such an act would constitute a violation of the Constitution’s double jeopardy clause. But one can be tried by a court-martial and a state court for the same offense. While this is rare, it is not unheard of.