Firearms — México
Bringing firearms, ammunition, or any instrument considered a weapon by the Méxican government in to México is illegal without a permit previously issued by the Méxican authorities. Violations may result in a stiff prison sentence. Accidental violations or being unaware of this prohibition will not spare you from penalties.
Most violations involve US citizens with illegal weapons driving automobiles or piloting private yachts south of the border on vacation. The prohibition extends to Méxican territorial waters. A sea vessel passing through Méxican territorial water, but not planning on putting in to port, is not exempt. Because of media reports in the U.S. the incidences of violations are way down. To inquire about getting a permit contact the nearest Méxican embassy or consulate.
According to the US Bureau of Alcohol, Tobacco, and Firearms 90% of the weapons used by the Méxican drug cartels are bought in the US legally and then smuggled illegally in to México. Given the government's recent hard-line stance with the cartels and the concomitant increase in violence, the Méxican army and police have been even more diligent in trying to stifle the flow of illegal weapons from the US.