I disagree, the constitution says specifically what should be done with US citizens who wage war against us. There is hardly any point in Section 3 clause 1 if it can be nullified by simply accusing someone of treason and locking them up indefinitely.

SECTION 3. Clause 1. Treason against the United States, shall consist only in levying War against them, or in adhering to their Enemies, giving them Aid and Comfort. No Person shall be convicted of Treason unless on the testimony of two Witnesses to the same overt Act, or on Confession in open court.

Any US citizen accused of such is entitled to their day in court.