Enforcement by the people assigned to do it: the Border Patrol.
Obviously, the Border Patrol cannot handle the load. The Feds really don't know how many illegals are in this country. They only can estimate. We need to take all military personnel, like from Camp Pendelton, and other bases in the South West and start protecting the border. We need to use the border patrol officers on inland assignments, and start deporting them.
Anyhow that is what I would do.