Last fall, the Navy Department had a controversial disciplinary case before it: Maj. Jason C. Brezler had been asked by Marine colleagues to submit all the information he had about an influential Afghan police chief suspected of abusing children. Brezler sent a classified document in response over an unclassified Yahoo email server, and he self-reported the mistake soon after. But the Marine Corps recommended that he be discharged for mishandling classified material. The Navy Department, which oversees the Marine Corps, had the ability to uphold or overturn the decision. However, rather than just looking at the merits of the case,...