No clue.Well okay then... but it still begs the question "Why?" Drugs? Training? Why the hell would they care if it's LEAVING Mexico, the US does a pretty good job if secondary is required. I don't see what this accomplishes other than pissing people off.
Who takes money OUT of Mexico? Hahaha! The bigger concern has always been drug money coming INTO Mexico. The drugs flow out, the money flows in, and so it goes. Meh. I'm clueless and I never have anything that could be considered contraband, so no biggie. Dig through my dirty underwear and fishy smelling clothes if you must.The USA does this often just before Canadian customs. Lot of times is for money. Could be the same here.