Let's review Mexican law.

Mexico has strict gun laws. Mexican citizens and legal residents may purchase new non-military firearms for self-protection or hunting only after receiving approval of a petition to the Defense Ministry, which performs extensive background checks. The allowed weapons are restricted to relatively low-caliber and can be purchased from the Defense Ministry only. "Military" firearms, including pistols with bores exceeding .38 caliber, and bb guns (but not pellet guns) require federal licenses and are regulated in a manner similar to that dictated by the U.S. National Firearms Act (NFA). The private sale of "non-military" firearms, however, is unregulated, and while these firearms are supposed to be registered with the government, in practice this is widely ignored. Laws dealing with the possession of "non-military" firearms are left to the states. Generally, "non-military" firearms may be kept in the home, but a license is required to carry them outside the home.