Transparency guarantees in Mexico presented a serious challenge to its 2007–2012 war on drugs. We use an original database of access to information requests, including both petitions for information and appeals to IFAI. We conduct statistical tests on the databases, finding that transparency is lower on security issues, as expected, but that there are unexpected variations between security agencies, and over time. We then conduct a content analysis of freedom of information requests to determine what drives agency responses, finding that security agencies developed various techniques to deflect petitions for information, such as falsely claiming that information has been provided when it has not, claiming that the information is outside the competence of the agency, that it does not exist, or that it is already in the public domain. Also there are significant differences in transparency between security agencies, possibly explained by their operational roles.