Note that the President could always leave standing orders even as he exits the door. Always possible he left a sticky note in a bunker somewhere saying martial law is in effect at 11:59 today and Biden is to be arrested at the podium. Until someone else takes office, under federal martial law the President continues his position until revoking martial law.

I mean, it's a long shot trying to smack a hail mary, but hopium doesn't come easy these days. >.>