There are plans to remove passports, with their accompanying entitlements, from those Britons who have gone abroad for jihadist purposes or return here after such exploits. Although it has been widely reported that this cannot be done under international law, there appears to be no international treaty that the UK has signed that would prevent this action. Deprivation is permitted under s.66 of the Immigration Act 2014, even if the result would be statelessness, provided that there are reasonable grounds to believe that the affected person is able to acquire the nationality of another state. The whole situation is explained in a Parliamentary briefing available here – http://www.parliament.uk/briefing-papers/sn06820/deprivation-of-british-citizenship-and-withdrawal-of-passport-facilities. If the action of deprivation were carried out, and challenged under human rights law, then Article 17 of the European Convention, repeated in our Human Rights Act 1998, is relevant:
“Prohibition of abuse of rights
Nothing in this Convention may be interpreted as implying for any State, group or person any right to engage in any activity or perform any act aimed at the destruction of any of the rights and freedoms set forth herein or at their limitation to a greater extent than is provided for in the Convention.”
That exemption may well be successfully pleaded by the government in defence. The right to retain British citizenship can hardly be relied on as a human right if the claimant wants to return in order to kill or injure people here.