>But making 12 million non-citizens suddenly citizens creates a problem today and many more tomorrow.

Why citizens? There must be other options. Make them foreign workers, make them pay taxes, but above all make them legal aliens, with a certain set of rights and obligations. And make that simple to do and simple to check.

Then the employers won't be able to skirt their responsibility - they would have a simple way to check, so they'd be paying huge fines if they didn't. The system would be able to keep tabs on those people, so they wouldn't be out of reach. Any criminal investigation wouldn't stumble upon dozens of people who don't want to meet the police because they're illegal. You wouldn't get hit by an uninsured car. Out of twelve million people, I assume at least eleven would gladly join the system and start breathing freely - and would occasionally go home to visit, knowing that they could return.

As for those among them who want to stay indefinitely, there should be a path to a regular green card, then citizenship after a number of years.

And then the remaining few dozen thousand who would still be illegal would be much easier to weed out.

If renting to a foreigner becomes illegal, then any foreign tourist with a clerical error in his paperwork may cause a lot of trouble to the leasing office. Also, anyone who comes here on business may stumble upon the stellar speed of the administration, overstay his visa waiting for issues to get solved, and become a criminal. Not good for business.