@Marignon: Your assertion about travel restrictions for scientists from the U.S. is incorrect.
There are export restrictions for certain classes of encryption technology still in place, but knowledge of these encryption technologies does not require your travel to be restricted.
I can say that my own parents are scientists and they do not have the right to go abroad even for tourism - only on a business mission.
If they'd wished to emigrate - they would not have been allowed to do so - just like Gulko - even nowadays.
I'm more than sure that there are hundreds of thousands of such people in the USA.