Much like the drug problem, you move to take away the demand, and you attack the supply.
The socalled war against drugs was a complete failure. It didn't shut down drug organizations, it didn't eliminate drug use, or even limit crime. It did jail thousands of drug users, particularly young black men and create a cycle of poverty.
Today, you have evidence that legalizing marijuana is cutting into drug cartels revenues and activities...
https://www.washingtonpost.com/news/won ... 7e94e8310e
And creating lots of tax revenues that are helping fund schools and hospitals..
What this indicates is that serious regulation at the employer level could lead to genuine control of immigration. Put a couple of meat packing presidents in jail for knowingly hiring illegal aliens and proper vetting of employees by employers will go way up. (Jail, for some reason, being a helluva lot bigger deterrent to millionaires than desperate immigrants looking for a low wage job to feed their family.)
At the same time, you have to be prepared to allow illegals who have had long employment to come forward and, with their employer, commit to a process of legalizing their status. Why? Because these illegals are too important to the economy to suddenly lose them. It would be like The Leftovers.... Entire sectors of the economy would be faced with labor shortages.