This chapter describes the major decisions that defined the way the Mexican system interacts with international investment awards. It is one example of the way the investment regime interacts with domestic courts in Latin America. The case of Mexico, however, is exceptional in that it has been highly influenced by the 1994 North American Free Trade Agreement (NAFTA) cases and its unique ‘waiver’ to initiate domestic proceedings provision. Other domestic judiciaries in Latin America, such as Colombia, have had the opportunity to engage in meaningful discussions on the constitutionality of investment treaties. As will be explained below, the substantive discussion on the constitutionality of investment agreements or investment chapters in trade agreements has not been discussed in Mexico.