You just serve notice to post-America's employers that they're in big trouble if they hire them.
Paul Mirengoff at Power Line:
. . . the idea that getting rid of millions of illegal immigrants would require house-to-house searches, dedicated trains to the border, etc., is wrong. In fact, all the federal government needs to do is enforce existing laws relating to employment. If a few farmers, contractors and owners of lawn services are sent to jail, the others will take the lesson quickly, and jobs for illegal immigrants will dry up. Most (not all, of course) will then leave the country voluntarily, the same way they came. The government doesn’t need to do anything other than enforce existing laws. This is what Mitt Romney referred to as “self-deportation,” a term that some found offensive for reasons I don’t understand.
Kevin Williamson at NRO:
As I have argued for some time, we could do a great deal to reduce and reverse illegal immigration by taking five fairly straightforward steps that do not even require building a wall (though there are sections of the border that certainly should be walled). Those steps are: 1) Passing a law that forbids anyone who is or who has been an illegal immigrant from ever becoming a U.S. citizen, even if his current status is legal; 2) Passing a similar law that forbids anyone who is or has been an illegal immigrant from applying for a work permit, even if his current status is legal; 3) Carrying out robust workplace enforcement through mandatory E-Verify and the deployment of asset forfeiture against businesses convicted of employing illegal-alien labor; 4) Putting a citizen or non-citizen stamp on drivers’ licenses and requiring non-citizens to document their legal status when engaging in ordinary financial transactions such as cashing a check or booking domestic travel; 5) Passing a law that forbids anyone who is or has been an illegal immigrant from ever legally entering the United States.Remove the primary motivation for coming here.