For a very long time the strategy around major events like the conventions has been to flagrantly violate the law by rounding up anyone and everyone they deem a threat, throw them in jail for a week, then let them out and drop the charges and eat the resulting lawsuits. "You can beat the rap but you can't beat the ride". Worth reading up on, I want to say the 08 RNC in Minneapolis. If I remember the lore correctly the cops raided some activist group and charged them with having molotovs because there were empty jars, rags, and a can of gasoline in three separate places in the house. The cops play real, real dirty. There's actually a whole fascinating history of this tied back to the cops losing control at the Battle of Seattle in '99 and the "Miami Method" policing that resulted from Seattle, and then that mutated in to modernized military policing as we know it.