Department of Pre-Crime

I quite enjoy the movie Minority Report based on a Philip K Dick short story though quite well enhanced by some good effects. It essentially involves the police using pre-cogs or precognitive telepaths who can predict murder before it even happens and so the pre criminals are arrested and locked up, at least until a flaw in the system shows how it can be fooled.
Still, even today the police were out arresting people for intentions rather than actual criminal acts.

Daily Mail.

Earlier, three protesters thought to have been planning to behead effigies of the royals were arrested in London.
Police seized a guillotine as they arrested two men - aged 68 and 45 - and a 68-year-old woman last night thought to have been plotting disruption on the day of the Royal Wedding.
It is understood one of the men arrested is Chris Knight, 68, head of the anti-royal anarchist group The Government of the Dead.
The arrests in Brockley, South-East London, come after officers warned there would be a number of pre-emptive arrests on the eve of the big day.

Ok, these people may well have carried through their attempts to disrupt the wedding, however planning something is not the same as doing, even if arrested as they were carrying a guillotine. Even then, that's a legitimate protest, granted they probably would have been lynched by the attending royalists, but, IT'S STILL NOT A CRIME! pre-emptive means by it's very nature that the police are arresting people who have committed no crime as yet and I'm fairly sure some human rights lawyer is going to have a field day over this lot once they get their teeth into it. Granted the police may have saved disruption on the day, but at what cost? I'm no royalist myself, bit of respect for the Queen, hell of a lot of respect for Prince Philip, but no respect at all for the rest of the hangers on especially the heir to the throne. To my mind though, they aren't worth a protest over, but should I have chosen to protest peacefully if noisily I might have been arrested. Even if on the day I chickened out, or was merely talking up a storm and had no intentions of doing anything. I'm not saying the people arrested weren't going to try and protest, however until they did they were guilty of nothing more than conspiracy and that isn't a crime, or rather wasn't until today. The police do however have a history of this, just ask football fans and striking miners about their coaches being turned around on mere suspicion.