A large proportion of those returning have been imprisoned. All are monitored by the security services who take a view on what kind of intelligence asset they may be. I don't think anyone is just getting back in and being left to it unless they are well and truly under the radar. It would have felt right to not allow them back in, but I doubt that we are allowed under international law to do so, because it would be dumping the problem. We would never get to deport anyone to anywhere. Sadly, it is individuals known but considered low risk who seem to be the danger at the moment. How the security services deal with them is a big challenge because it is hard to know what is in their minds. How did they become 'known'? It may be that they have committed offences or further offences can be framed that would allow intervention. I'd be for a zero tolerance for flirting with extremism.