Mexican matters

Mexicanlaws.com has some very useful free content on its webpages. With my level of ignorance I found the page What is the difference between a Law, a Regulation, a NOM, and a NMX? illuminating.
It also explains why I was encountering differences in citations to Mexican environmental NOMs – some included “ECOL” others “SEMARNAT” – now I know it just reflects a change in name of the government secretariat in charge of that area of law.