High Quality Content by WIKIPEDIA articles! Judge Advocate General`s Corps, also known as JAG or JAG Corps, refers to the legal branch or specialty of the U.S. Air Force, Army, Coast Guard, and Navy. Officers serving in the JAG Corps are typically called Judge Advocates. The Marine Corps and Coast Guard do not maintain separate JAG Corps per se and judge advocates in those services maintain their line officer-status. In the Army and Navy, JAG officers only serve in legal positions.