They had all lived in America and spoke perfect English. Two of them ended up defecting and turning the other six in to the American government. They had been trained in sabotage at a school near Berlin and were carrying explosives when apprehended. The Germans requested them to be tried in open courts, but the court rejected the request: "Lawful combatants are subject to capture and detention as prisoners of war. Unlawful combatants are likewise subject to capture and detention, but in addition they are subject to trial and punishment by military tribunals for acts which render their belligerency unlawful" (Savage, A5). The Nazis were put to death by electrocution, and the defectors were jailed. .
Other presidents have tried to exercise this same power in the past. George Washington held a military trial for a spy, but he did it before the constitution was written. Abraham Lincoln actually suspended habeas corpus in places and authorizing military trials without Congress's consent, but he later did go to them for approval only to be denied by the Supreme Court. Andrew Johnson and Richard Nixon both stretched the law without legal reason. Franklin D. Roosevelt put Japanese-American citizens in camps with the court's approval. Now it's George W. Bush's turn to see exactly how far he can bend the laws in times of war.
At this point Bush has set up an interesting set of rules for these military tribunals. The trials may take place in the U.S. or on naval ships (either way the trials are private), hearsay can be used as evidence, the defendant doesn't have the right to challenge the evidence, and may not even get a lawyer of his choice. Guilt doesn't need to be proven beyond a reasonable doubt, only two-thirds majority is needed to execute a suspect, and there may not be any chance to appeal. Of course Bush would have to personally designate which suspects are to be tried in military courts.