I hadn't heard it seriously proposed by anyone. It is just a PC BS reaction to calls for a fence and tighter security along the Southern border with Mexico.
Better than any fencing would be to recall all of our military from around the globe, close every base we don't need in the US and place bases and personnel along both borders.
The reason for the northern bases isn't because there is any problems with snow-backs but to give us bases to train our people in every imaginable terrain. They could work in full combination with Canada and make both countries stronger.
Equally important is to set up things like E-verify and routine ID checks when other inspections are made at business and construction sites.
We also need a approved worker plan that lets people work in agriculture or other industries that can show an inability to cover their needs with American workers. Those employers, however, need to pay for their health care and education rather than leave the taxpayers holding the bag for the billions in costs.