Registries do not work. So what, they’re on a registry. Is that going to somehow stop them from murdering, raping, instituting Sharia? No. Send them back.
It’s to give you a starting place when you’re looking for them.
It also gives you family members that could be sympathetic to ‘the cause’.
These are foreign nationals, and I see nothing wrong with keeping tabs on them.
It’s part of the Visa process.
As I understand it, people are asked why they are traveling. If they say to visit, they may be asked who and where.
I see no problem with that.