Originally Posted by Ursa major
I think the rules may have changed since then. Governments on this side of the Atlantic have allowed various agencies on your side very wide access to data about us (whether or not we're travelling to the US). If the person involved here can circumvent all that and arrive in the US, I doubt a friendly (but costly and basically unnecessary) word from any number of otherwise desk-bound UK police officers is going to do the trick.
Over there, you also have had your money wasted on this sort of thing. Well, almost the same: by which I mean making sure certain (alleged) murderers were never returned to face justice on this side of the Pond.
It may not, but it may scare them into quitting or convince them they're being watched too closely to pull it off. Or it may just keep them out of the country and unable to act on it. And no matter how much information they could get from the UK, that's no substitute for actually seeing the person. A background check probably turns up little other than his age and criminal record and maybe some financial info, which tells law enforcement nothing about whether you may actually act or not. It's probably a waste of money and time and 99% of the people you interview or investigate are harmless, but it's the way the secret service operates. It's been like this for a long time... if you threaten the US president, you're going to have US agents knocking at your door.
Anyway, my point wasn't the wisdom (or lack thereof) of the response, just that I don't think this story signifies some draconian censorship measure to stifle any criticism of the president. If you watch Foxnews in the US these days, it's clearly open season for criticizing the president. The visit was a response to the threat, not to name-calling or an attempt to stifle political speech, as it was characterized in earlier posts. That's all I'm saying.
As to the alleged murderer... are you thinking of a particular case? I'm intrigued.