The word “requirement” bothers me also until I link it to the title of Sec 1032 that is “Requirement for Military Custody”. So then I see how any reference to U.S. citizens just disappears.
But then I can also see your points about how failing to include a passage that says something like “no way in hell” is also a problem.
Words have meaning, as does a lack of words.
Without words specifically prohibiting it, it is allowed.
Remember, this allows the military to do this. POTUS is CinC. Whether a person is a citizen, all it takes is for him to be defined or determined to be a ‘terrorist’ and it is time for jail.
Remember, early in this administration, DHS defined potential terrorists - ex-military, right wingers, Christians....
The groundwork is laid.