In the case of McElroy, Secretary of Defense, et al. v. United States ex rel. Guagliardo (1959), the Supreme Court ruled in favor of Guagliardo, a civilian employee working for the U.S Navy overseas who was charged with embezzlement and larceny under military law by court-martial despite his civilian status. The central issue revolved around whether civilians could be subjected to military jurisdiction while accompanying armed forces abroad during peacetime. The Supreme Court held that Article 2(11) of Uniform Code Military Justice (UCMJ) did not extend court-martial jurisdiction over civilians serving with armed forces in peacetime; it only applied during times of war or declared emergencies as per historical precedent and legislative history. This ruling emphasized that constitutional safeguards should not be set aside lightly even when dealing with matters related to national security or foreign policy interests.

In the dissenting opinion for McElroy, Secretary of Defense, et al. v. United States ex rel. Guagliardo, Justice Frankfurter disagreed with the majority's interpretation of 50 U.S.C § 403a(7). He argued that this statute does not grant civilian employees working overseas a right to trial by court-martial for crimes committed abroad; instead it merely allows military authorities to arrest and hold them until they can be tried in a proper court. The justice believed that Congress intended these individuals to be subject only to local jurisdiction or returned home for prosecution under American law if necessary. He also pointed out that civilians have historically been excluded from courts-martial except during times when martial law is declared or in occupied enemy territory where no civil authority exists - neither condition applied here.