Where should drug smugglers in uniform be tried?

SNS Juan Sebastián de Elcano

Six crew members of a Spanish Navy training ship, plus the ship's civilian cook, have been charged by a military judge in connection with drug smuggling. Details here. Drug trafficking is of course a crime under Spanish civilian criminal law. It's certainly not crazy for the uniformed personnel to be tried in a military court, but why not just send them downtown for trial? A fortiori for the cook.