Are there most likely small illegal shops? Absolutely. But he is correct. There is only one single legal firearms store in mexico city and is run by the military
There are two in the whole country. Finding that odd shows a very Americanized view where gun are ubiquitous instead of controlled which is the exact point of this article.
Not American and I'm still baffled by that. I can think of two in my "small for US standards" city, in a country with less people than Mexico city, although most of their business is for sports and hunting.
Ask for anything slightly large or automatic and they'll laugh all the way to a cell.