The U.S. Supreme Court case O'Callahan v. Parker, Warden in 1968 revolved around the issue of whether a member of the armed forces could be court-martialed for a crime committed off base and not during active duty. The petitioner, O'Callahan, was an army serviceman who had been convicted by a military court for attempted rape and burglary while off-duty in Hawaii. He argued that his offenses were unrelated to his military service and thus should have been tried in civilian courts under the Fifth Amendment's guarantee against double jeopardy. In its decision, the Supreme Court sided with O’Callahan ruling that members of the U.S. Armed Forces cannot be court-martialed for crimes committed outside their official duties or off-base premises unless it is directly connected to their service responsibilities or affects military discipline orderliness significantly. This landmark judgment established what came to be known as "the service connection" test which later got overruled by Solorio v United States (1987), reinstating Congress’s plenary power over military justice.

In the dissenting opinion for O'Callahan v. Parker, Justice Harlan argued that military jurisdiction over service members should not be limited to service-connected offenses. He contended that the majority's decision undermined the ability of military law to maintain order and discipline within its ranks. According to him, a soldier does not cease being a soldier just because he is off duty or away from his post; thus, it was inappropriate for civilian courts to interfere in matters concerning soldiers who had committed crimes while still enlisted in active duty. Furthermore, he believed that this ruling would create unnecessary confusion about when and where military law applies as well as potentially jeopardize national security by weakening military authority during times of war or emergency.