Immigration is one way only. You can encourage them to emigrate back to the country where they hail from, but that only really works with higher-skilled immigrants. The worst of the worst stay, because they've got nothing else going for them.
So you enforce your laws, and any who are unable to live in a country that's not slowly being turned into a Caliphate will get tired of being imprisoned again and again for threats and intimidation, and leave.
Immigration is one way only. You can encourage them to emigrate back to the country where they hail from, but that only really works with higher-skilled immigrants. The worst of the worst stay, because they've got nothing else going for them.
So you enforce your laws, and any who are unable to live in a country that's not slowly being turned into a Caliphate will get tired of being imprisoned again and again for threats and intimidation, and leave.