I'm not sure if I'm joking. In any case, the writ of habeas corpus is the legal tool that a court can theoretically use to compel the appearance of a prisoner before it. It is the legal doctrine that underlies the right to trial, and I say "theoretically" because courts rarely need to issue one; it's just standard procedure to bring people to court to face charges.
By suspending it, Abraham Lincoln could detain those people he deemed dangerous seditionists indefinitely, because the detainees would have to go to court to challenge their detention, and there was no way to get to court. The effect of suspending it again is that it wouldn't matter that Baboon (autocorrect and I'm leaving it) and Stone were pardoned, or that there were even criminal charges.
Lincoln did it, George W. Bush did it. Barack Obama did it. The Constitution contains a clause which allows it to be suspended due to rebellion or threats to public safety. It's a dangerous thing to allow a president to do, but the MAGA danger might be greater.