Sure, but then why do they have to wait? ICE agents who want to threaten legal observers can just do it to their faces - as we've seen, even if they murder legal observers the Trump regime will have their back. I think most don't want to do that, whether out of cowardice or an understanding of what's coming once their leaders are brought to justice.
They are continuously moving the goalpost. They don't know themselves what they are gonna get away with for the time being. But they will iterate themselves to whatever is the line - or don't stop if there isn't any.
But there aren't that many of them. But if you make the populace afraid in advance, that's cheaper than deploying a batch of goons to every major city.