Five Mexican states are mounting a supreme court challenge to the new marriage equality law passed in Mexico City.

The Mexico City assembly approved same-sex marriages in December, passing the first such measure in Latin America. The law is scheduled to take effect in the city in March.

According to Agence France-Presse, the five states planning the court challenge have governors from the Nation Action Party (PAN) of President Felipe Calderon. Elements within PAN have vocally opposed marriage equality.

The five states of Guanajuato, Jalisco, Morelos, Sonora, and Tlaxcala are taking action because they are concerned that the Mexico City law could oblige them to recognize same-sex marriages, according to AFP.