The Blair government says it will take measures so that any foreigner - anyone who is not a British citizen - who is jailed will then be deported.
Only in the most extreme cases will the risk of being killed or tortured in their country of origin prevent deportation.
The government's proposed measures are a real threat to the labour movement, and racist too.
Any foreign-born worker who becomes active in a trade union, then falls foul of the police on a picket line or demonstration and gets a jail sentence for some such offence as "obstructing a police officer in the course of their duty" (which can get you up to a month in jail), will be liable to be deported, even if that means a probable death sentence.
The racism comes in the double standards. First, in the unspoken assumption that non-British-citizens who serve out a jail sentence are intolerably dangerous after they have finished their sentence, whereas British citizens who have been found guilty of exactly the same offence and served exactly the same jail sentence are OK.
And in the unspoken assumption that if these non-British-citizens are dangerous, then it is all right for them to be dangerous in another country, but intolerable for them to be dangerous here.