Yes they are.
This is a complicated area, and there has been a lot of word-fudging in spinning this subject. So bear with me as we take things step by step.
* The U.S. Constitution generally guarantees the “Privilege of the Writ of Habeas Corpus.” The writ of habeas corpus is a court order a prisoner can obtain requiring the jailer to come into court and justify his detention of the prisoner. It is a traditional way in which those held can demand a fair trial by jury in a civilian court. The writ of habeas corpus is a treasured part of our traditional liberty. Belief that the British were infringing it was one cause of the American Revolution. (The writ is called a “privilege” rather than a “right” because it is a creation of the legal system rather than a natural right, like the right to free speech.)
* By the Constitution’s original meaning, the privilege of habeas corpus is guaranteed to all those in “allegiance” to the United States. “Allegiance” is an old technical legal term that includes both citizens and aliens legally in the country.
* By successfully convincing a judge to issue a writ of habeas corpus, citizens, foreign visitors, and legal residents may obtain a hearing that may induce the judge to order a civilian trial. It matters not how heinous the crimes they are accused of. For example, a person charged with trying to blow up a building on behalf of a foreign power can be charged with treason. But while still merely accused, he is entitled to all the protections of due process, including a fair, public trial before a jury of his peers.
* By the Constitution’s original meaning, habeas corpus does NOT apply if the Congress, as an incident to its war power, “suspends” the writ for a particular time and place. However, the Constitution says that Congress may “suspend” the writ only “when in cases of rebellion or invasion the public safety may require it.” Congress has not suspended the writ, and it is doubtful that occasional acts of terrorism constitute a sufficient “rebellion or invasion” to justify doing so. Even if Congress could suspend the writ, a Bill of Suspension would be a serious, much-debated measure for which Congress would have to assume direct political accountability. Political accountability is not a big priority with Congress right now.
* Members of all belligerent armed forces (both sides) are subject to military, not civilian, law.
* Thus, by the law of war, the executive (and the military officers under him) may incarcerate for the duration of the conflict any enemy combatants captured in the theater of war.
* By the Constitution’s original meaning the executive has no co