Mexico has approved a constitutional amendment banning the domestic cultivation of maize that has been genetically modified (GM). However, the country does not cultivate GM maize and has upheld a restriction on cultivation since 1998. Transgenic maize varieties will require an evaluation to ensure they are free of threats to the biosafety, health and biocultural heritage of Mexico and its population. The amendment formalises existing restrictions on the cultivation of GM maize in Mexico. However, it remains unclear whether the scope of the restrictions extends to other uses, such as maize imported for food, feed and processing.