In which situation may a service member not refuse an Article 15 and demand a court-martial?

The situation where a service member may not refuse an Article 15 and demand a court-martial occurs specifically when the member is aboard a ship. This is due to the unique operational environment and command structure present in naval operations.

When a service member is on a ship, the command can impose non-judicial punishment through an Article 15 because of the immediate need for discipline and order in the confined, operational space of a vessel. In such circumstances, a court-martial could be deemed impractical, as it involves more extensive procedures that could disrupt the ship's mission and readiness.

In contrast, the ability to refuse an Article 15 may remain available to service members stationed overseas or in a war zone, depending on the circumstances, as these situations might not impose the same immediate necessity for command control as being aboard a ship. Thus, the correct answer is anchored in the understanding of military necessity and the distinct context of naval operations.