Captain Brittany Warren, a US Army JAG who has just completed her JD at GW Law School, has an article appearing in the Military Law Review (Vol. 212, 2012, p. 133, link is to jagcnet.army.mil), "The Case of the Murdering Wives: Reid v. Covert and the Complicated Question of Civilians and Courts-Martial." It's a fine article, and one that puts Reid v. Covert into an important historical as well as contemporary perspective, with respect to the question of civilians in military courts.
The article's historical discussion, starting with British practice before the American Revolution down to the 1950s, when the events of Reid v. Covert took place, notes that Britain of the 17th and 18th centuries, "three classes of civilians typically accompanied a British army during times of war: retainers, which included servants, volunteers, and women and children; sutlers, who sold provisions like tobacco and coffee to armies in the field; and civil officers and civilian employees of the military." Each was subject to court-martial at various times; and in the 1740s, Warren says, a new "camp follower" provision was added by Parliament to the Articles of War:
All Suttlers and Retainers to a Camp, and all Persons whatsoever Serving with Our Armys in the Field, tho’ no inlisted Soldiers, are to be Subject to Orders, according to the Rules & Discipline of War.
"In the field" is a term of art referring, Warren says, to a "time of hostilities when military operations were underway." The additional language was intended to ensure that civilians who supported or were otherwise lawfully present "in the field" and who were not otherwise subject to civilian law - given the fact of hostilities displacing civilian law either of the locale or metropolitan British law - would be covered by a body of law. Camp-followers were regularly tried in this system, including wives of soldiers - and indeed on 1778 case dealt with a soldier's wife who plundered in violation of the articles of war, was given 100 lashes and "drummed out of the Army."
Captain Warren goes on in the main body of the article to address the complications of civilians in military courts following WWII and the passage of the Uniform Code of Military Justice - the setting in which Reid v. Covert arises - including all the complications of Status of Forces Agreements, and so on. It's a fascinating article, filled with intriguing details.