I think they can westwind. Keep a N reg in Russia etc. Even if it was illegal the type of persons that own said hardware over there isn't looked at to often.
Its the same in the Middle East as well. Shiek ma bob can keep a N reg for as long as he likes. Mear mortals would have to go local after 6 months.
Not that its really an issue because the whole reason for having these machines down there is to escape the bloody place so they tend to move around alot.