Invasive exotic species have been identified worldwide as a major threat to biodiversity. Legal instruments are an important tool in counteracting their negative impacts. There are four important aspects that any legal instrument should have, that is: an explicit (and transparent) method for species inclusion; an exclusive focus, so that conflict between different pieces of legislation does not occur; be dynamic and able to be frequently updated; and be the clear responsibility of a single responsible authority. We examine these aspects with regard to the most recent Agreement of invasive exotic species published by the Federal government of Mexico. In doing so, we outline six crucial aspects that any species included on a list of exotic invasive species should have prior, that is: a clear taxonomic determination at species level, with a list of synonym or synonym database linked to the list; an accurate delineation of native and invasive ranges of species included; an assessment on the degree of invasiveness and impacts of the species; the establishment of temporal introduction baselines; and inclusion on the list based on a scheme of threat prioritization. If these legal and species list requirements are ignored, such as in the Mexican legislation and Agreement, the usefulness of the legislation will be compromised and may actually be harmful to native taxa.