This anon has an MA in international law, so a thought here:
RE the 13 page 2002 memo from the AG office. Note the distinction between Quirin & Milligan. Both were US citizens. Both were involved with bad guys. One was not able to be held by the military (yet subject to trial in domestic courts), one was able to be held by the military. It is not enough to be a sympathizer, as was Milligen. You must be an active belligerent: Quirin was a (Nazi) “saboteur”. The Dec 2017 EO was specific to freezing finances and other assets, and did not reference the military. This is very different.