Jose Padilla "
That's actually not true in all circumstances.
For instance, prior to WW2 Adolph Hitler put out a call for all true Aryans worldwide to come defend the Fatherland. More than 1,000 American citizens answered his call by going to Germany and enlisting in the Wehrmacht (Army).
But then after Pearl Harbor, Germany declared war on the U.S. There were now American citizens in Germany at war with America herself.
When our soldiers encountered these American citizens, they were shot on sight on the battlefield, or captured and imprisoned as prisoners of war.
But interestingly enough, the Surpreme Court ruled that those American citizens were **NOT** entitled to the protections of the U.S. Constitution. So those "American" POWs were not given attorneys. They could not sue for bail. They could not call witnesses. They were not entitled to trials.
Later, a small group of those Aryan-Americans were brought to the U.S. mainland by a German U-boat to conduct sabatoge. They were dressed in civilian clothes, and they were captured by American police, not military forces.
Again the U.S. Supreme Court ruled that such battlefield combatants, even though some were American citizens, had no civilian rights under the U.S. Constitution. They were given military trials/tribunals, and several (but not all) were executed.
So, can U.S. citizens be detained without trials and without attorneys? Well, the answer, historically at least, has been "yes" if they are battlefield cambatants.
One of the 9/11/01 terrorists was an American citizen, for instance. Certainly there would have been no crime if an innocent American on his hijacked aircraft had executed that particular person without trial, even though the perp in question was a U.S. Citizen.
Nor do we stop battles, either in America or in foreign lands, to give U.S. citizens like Taliban Johnny a trial or an attorney. Such battlefield combatants are dealt with at our convenience, under such rules and procedures as we deem necessary.
The moral to this story is that taking up arms **against** America is a good way to lose your Constitutional protections.