They need to seperate the wheat from the chaff.
Any immigrants caught committing a crime should be instantly deported with no questions asked leaving the honest ones to remain.
This is a strong answer but maybe not a bad one on several conditions:
-First the states should guarantee employment for its whole population (I'm not talking about refugees, I'm talking about everyone). Anyone with a brain can understand how easy it would be to reduce unemployment to nearly 0, some reports revealed by wikileaks show government officials saying they want to keep unemployment rate at a relatively high level just for companies to keep low wages.
-second education should be reformed, you can't take the millions of migrants ( not just the recent ones, all of them) put them all together and saying "they don't adapt!" Of course they dont, why would they you put them all together!
-third reform construction and property ownership. No one should have the right to leave a house not rented for 20 years while people live in the street. That's the case for most bank properties (again around 30% of Paris buildings for example)
The you have to explicit a bit the notion of crime. For example in Switzerland they wanted to vote a law saying goes any migrants committing 2 crimes should be expelled, but it didn't pass because in Switzerland paying your taxes late is categorised as a crime, overspending is considered as a crime...
So if you explicit the notion of crime as a physical agression for example, then why not. Why not instaurant such law, a bit harsh but it's not bad in itself.
You should also reform the way to get nationalities, in france you have people actually working and paying good taxes for 10 years who still don't have French nationality, I don't think it's normal! ^^