So you stand by until something happens. ID checks aren't Constitutional down here. They have to be supported by reasonable suspicion that the person (not the crowd) has committed, is committing, or intends to commit a crime.
Trespass also isn't a crime. It's a civil matter. It only becomes...
The DC cops are smart. George Washington University asked them to clear a camp, and the cops said "Nope. They're students, they're entitled to be on campus, and they aren't being violent or breaking the law."
He's walking a narrow line. He's done stuff I disagree with, and stuff I agree with. So far I'd call him a mid-rank Speaker with the potential to be a really good one. Time will tell.