No, he broke the law. The news stories are very skewed but they were the only ones I could find in English. First off, Guns are illegal in Mexico and he knew it. He thought he could bring it with him to get a license but he would not have gotten a license anyway. Furthermore, the US is on very thin ice with Mexico already over bringing guns in (see Fast and Furious).
There are signs like this on every road leading into Mexico. Why do so many Americans think they are an exception to the law?
i think the bolded part is where you missed the mark, i don't think they think they are exceptions but rather assume there are proper measures you can take to meet the requirements of the law while still not forfeiting something we have become very accustom to here in the US.
Here, normally, there is a permit for nearly anything if you are willing to pay for it and have a clean record.
what % of Mexicans that are in the US know all the laws (and they have presumably lived here for some time). Obviously there are plenty of signs on your way to Mexico to inform you about guns tho, but like i said most assume there is a permit they can buy and are accustom to having the right to approach an authority and willing clear up any lack of understanding without being made an example of.
an example of this would be the numerous "old" people who have accidently grew pot in there flower gardens only to later realize its illegality and are never prosecuted. Some have even called the cops on themselves after getting tipped off about what the plant was. we have become accustom to reasonably rational reactions here in the US and that's just not how it works in Mexico.
