With same-sex marriage law, Mexico City becomes battleground in culture wars

"Just because something has become common, should it be legally recognized?" said an editorial in El Semanario, a publication of the Catholic Archdiocese of Guadalajara. "If so, we should legalize all of the murders, narcotics traffic or whatever other activity that has become common."

Gay rights activist Mariana Pérez Ocaña said she fears conservative provincial leaders will chip away at same-sex marriage.

After abortion was legalized, she noted, states altered their constitutions to say life begins at conception. Governors affiliated with PAN have promised to challenge same-sex marriage.

"Many activists in gay groups fear there will be a backlash," Pérez said.

Binational couples will add to the legal complications, she said. If Pérez weds, the marriage will not be recognized in her partner's native California. Mexicans who marry partners from countries that recognize same-sex marriage, such as Spain and Canada, could ask for citizenship, but their spouses would not be eligible for the same in Mexico, she said.

"If a heterosexual couple gets married, they're automatically eligible for citizenship," she said.

Still, "marriage is a significant milestone," Pérez said. "This law is a very important step forward."