According to the Mexican copyright law (23-07-2003), Article 14, case 7 & 8: "Copyright shall not apply to shields, flags or emblems of any country, state, municipality or political division; names, acronyms, symbols or emblems of international governmental organisations, or any other organization officially recognized; or legislative, regulatory, administrative or judicial texts, as well as their official translations."
Hence it is assumed that this image has been released into the public domain.