A year after St. Paul police rounded up and arrested over 200 people who were planning to protest the Republican National Convention - but hadn't actually done anything yet - 27 plaintiffs filed a class action suit against the city on behalf of all those arrested. Police officers used pepper spray, non-lethal ammunition and horses against the protesters, none of whom was convicted of anything except not liking Republicans.
I remember watching Minority Report when it came out in 2002. It was topical. The U.S. was already well into justifying preemptive war, so it wasn't much of a stretch to imagine preemptive arrest. And of course it happened. I wonder how many peace protesters will get arrested this fall during anti-war demonstrations. Preemptively or not. Tom