There’s just one place in all of Mexico where you can legally buy a gun. It’s tucked away in an anonymous building on an army base in the capital, staffed by soldiers.

Those who enter must surrender any cellphones, tablets or cameras, remove caps and pass through a metal detector. Weapons are kept in locked glass cases, unlike many of the 50,000-plus U.S. gun shops where used-gun racks on showroom floors allow easy access and clerks are happy to let you heft an unloaded firearm.