To understand the legal nature of the Mexican petroleum license, one needs to review the history of the constitutional treatment of hydrocarbons. The regulation of the sector is a constant tension between a deep-rooted policy of government control over the resource motivated by nationalism, and the need to attract and maintain foreign investment to keep production flowing. According to the Constitution, only the State is empowered to extract and develop hydrocarbons. The secondary legislation, however, creates a contractual structure that allows the government to transfer the hydrocarbons to private parties at the wellhead.