It's "permanent" only if they allow it to be.
This is a complex issue, with the immigrants being both perpetrator and victim. The first thing I would do is resolve to not rebuild the projects that isolate the immigrants and create this culture. The immigrants continue to destroy the buildings, and the government keeps replacing them. Just condemn and knock down the buildings one at a time as they become uninhabitable. This will force the residents out, into the mainstream of the cities. I would not build new projects for them anywhere, they must disperse, and integrate with the rest of France. For those who can do that, fine, for those who won't, build extra prisons, maybe the size of the projects themselves. And the choice will be with each immigrant to integrate, or not.