Crossing into Tijuana, B.C., on a constant basis, I was given a week-long Visa each time. Didn’t ask for one (just visiting for a few hours) yet it was as simple as a Passport and 2 minutes of your time. Anyone with a passport could be a “legal” citizen just by crossing out of and back into the border crossing once a week.

I have gone through 5 other border crossings into Mexico and none of them had anyone to stop and assure Mexican citizenship. Pretty soft border protection compared to the U.S. which doesn’t really seem too strict. Their actual laws may be stricter (I am not sure), but their borders are much easier to cross “illegally” than U.S. from hundreds of personal experiences doing so.