Since Mexico is severely strained by the US returning a lot of hardcore criminals at once, the solution might be to create buffer prisoner holding facilities, essentially prisons, just north of the border.
It is tricky legal ground, because they are often criminals who have served their time in US prisons, but are Mexican citizens and need to be repatriated. So this would have to be a detention prison, releasing them back to Mexican authority only at a rate they could take.
As a far better alternative than letting them run wild up here.
Ironically, the area where they would be kept would be the equivalent to a “duty free area” in an airport. They would be considered “in transit” and under the jurisdiction of the CPB.
As with the Tom Hanks movie, The Terminal, they would be kept in the gap between nations.
Good idea...