Have people arrested, imprisoned, deny them a trial?
Ding, ding, ding, ding. Bingo. It is called violating Habeas Corpus. It is the clear difference between authoritarian dictators that rule by fear alone, and a democratic government that rules by law. He has purposely denied people due process, and is actively trying to deny jurisdiction to any judge who wants to review such detention.
It is the worst crime that a president can do, and he has done it in less 90 days.
Habeas Corpus.