Well, you can’t very easily put 5 million people in jail, just like that.
But they need to do something. Most obviously, they need to jail the people who hire these illegals and stop giving them aid and welfare. If they can’t find jobs or free lunches, they will be less eager to come.
Those who commit other crimes need to be jailed, but that, too, is a burden on the taxpayers. Better to keep them out to begin with.
Exactly. Vigorously prosecute the business that hire them. Make it extremely costly for businesses, and these folks won't get hired. With job opportunities dried up, they'll deport themselves.