Honor system for mexican border crossing. You couldn't make this stuff up. A simple way to remove all controls on crossing altogether. Millions will pour in here and at many other planned points of surrender. The Obama bolshevists will be spending money in mexico to tell the inhabitants where and how to cross.
The only thing worse than throwing open the border to a massive invasion of criminals would be arming them. You know, by actually stocking your invader army with military grade weapons so they would ... oh, wait. They caught them doing that, too.