|Alex Alí Méndez Díaz|
The requirement on judges resulted from a 2015 ruling by the Supreme Court of Justice of the Nation (SCJN) that declared all bans on marriage equality unconstitutional. The Supreme Court, however, has no power to end all states' bans simultaneously, and can only force individual states' bans out of existence in specific situations.
The ruling says: "Marriage. The law of any federative entity that, on the one hand, considers that the purpose of it [marriage] is procreation and/or that defines it as that which is celebrated between a man and a woman, is unconstitutional." ("Matrimonio. La ley de cualquier entidad federativa que, por un lado, considere que la finalidad de aquél es la procreación y/o que lo defina como el que se celebra entre un hombre y una mujer, es inconstitucional.")
The SCJN ruling resulted from a project by activist-lawyer Alex Alí Méndez Díaz and his organization México Igualitario that involved getting enough identical cases before the Supreme Court from multiple states to create an opportunity for the court to declare "jurisprudence" against bans on marriage equality.
Below are the states where same-sex couples can marry normally. Fourteen states and Mexico City have passed marriage equality legislatively, four states have marriage equality because Supreme Court rulings against their individual bans overrode their laws, and two states decided administratively to stop enforcing their unconstitutional bans.
• Aguascalientes (SCJN ruling)
• Baja California (administrative, then legislative)
• Baja California Sur (legislative)
• Campeche (legislative)
• Chiapas (SCJN ruling)
• Chihuahua (administrative)
• Coahuila (legislative)
• Colima (legislative)
• Hidalgo (legislative)
• Jalisco (SCJN ruling)
• Mexico City (legislative)
• Michoacán (legislative)
• Morelos (legislative)
• Nayarit (legislative)
• Nuevo León (SCJN ruling)
• Oaxaca (legislative)
• Puebla (SCJN ruling, then legislative)
• Quintana Roo (administrative)
• San Luis Potosí (legislative)
• Sinaloa (legislative)
• Tlaxcala (legislative)
As to states whose bans are dead because of Supreme Court rulings, here's what happened: When any law is passed in Mexico and takes effect, there is a 30-day window for certain governmental entities to challenge the law with an "action of unconstitutionality" at the Supreme Court. In all but one of those states, legislators made changes to their marriage laws, unrelated to marriage equality, and the revised paragraphs also included existing man-woman language. The revisions qualified as "new" laws that could be challenged during the 30 days after they took effect. The National Human Rights Commission filed actions of unconstitutionality against the man-woman language and the SCJN struck down the states' bans in separate rulings that began in 2016. The states likely were unaware they were setting up their same-sex-marriage bans for strikedown.
In the case of one those states, Aguascalientes, the challenged new law dealt with the health-care and pension system for state-government workers, and the National Human Rights Commission successfully argued to the SCJN that health care, pension and marriage laws are so dependent on each other that the man-woman definition of marriage, which was not new, needed to be tossed out as well. The SCJN invalidated all state laws that defined marriage as between a man and woman in 2019.
Going forward, it is very likely that additional state congresses will pass marriage equality — because ultimately their lawbooks need to reflect the 2015 Supreme Court jurisprudence ruling — and, in the meantime, it is possible that officials in additional states could stop enforcing their unconstitutional bans by administrative fiat. In addition, some other states' bans may be individually terminated by the Supreme Court via varied ongoing legal actions.
Beyond all that, in December 2019, the ruling Morena party proposed a federal constitutional amendment under which any state that hasn't passed a marriage-equality law must do so within three months of the amendment taking effect. The amendment also would invalidate all remaining state bans on marriage equality the moment it takes effect and extend to all civil-union couples, retroactive to when they entered the union, every right and obligation of marriage. Only 14 of the 20 states with marriage equality (and Mexico City) arrived there by passage of a law, so the amendment would force the hands of 17 states. Amending Mexico's constitution requires a two-thirds vote by members present the day of the vote in the federal Chamber of Deputies and the Senate of the Republic, followed by ratification by more than half of the 32 local congresses (31 state congresses and Mexico City's).
ADOPTION: Same-sex couples have adoption rights nationwide. The Supreme Court reiterated its jurisprudence in 2016, writing: "ADOPTION. The best interest of the minor is based on the suitability of the adopters, within which are irrelevant the type of family into which [the minor] will be integrated, as well as the sexual orientation or civil status of [the adopters]." ("Adopción. El interés superior del menor de edad se basa en la idoneidad de los adoptantes, dentro de la cual son irrelevantes el tipo de familia al que aquél será integrado, así como la orientación sexual o el estado civil de éstos.")