The first step are policies that encourage self deportation when neither jobs nor welfare are available. If some immigrants have done an honest respectable job as Americans I would support giving them a second chance to come back.
Such a problem always comes down to logistics when tens of millions are involved. Easier said than done.
Americans need to understand that the political and financial elites want most legacy Americans turned into an under class, only so that elites are turned into a bigger over class.
Yep, no jobs and no welfare goes a long ways toward solving the problem.
After that, every one encountered by any kind of cop, and every one who shows up at a hospital...it's ADIOS.