Just id them and they do not get citizenship. If they don't like it, they can leave.
Here's a crazy idea: we could also make the IDs and the visas temporary, so that after 6 or 8 years they go back home. I mean, it used to be called a "temporary worker program", so why not make it temporary?
I know that's "thinking out of the box" and a loopy idea, but it's one I heard from President Bush back in 2004.