It could be used as an excuse for anything, even Martial law. Start with troops on the border, heck they could even catch and release the illegals. Catch them, inject em with a nano GPS transponder, let them go and the immigrant tracking system is in place.
After a few decades admit to useing the tracking devices, and claim them safe for human use. There by getting a foot in the door, for other uses of
tracking via GPS implants. Other than the cell phone GPS that already is, come on if they are giving phone records of calls, surely cell phone records
will include positions too.