While traveling in Mexico, two Vatican prelates have criticized Mexico City's new gay marriage law.

The marriages of gay and lesbian couples are an imitation, the bishops said, Mexico's El Universal reported.

“A gay relationship is like decaffeinated coffee, you do not wake up,” Father Gonzalo Miranda, a bioethics professor at Regina Apostolorum University, a pontifical university, said.

Miranda, along with Monsignor Elio Sgreccia, president emeritus of the Pontification Academy for Life in the Vatican, are in Mexico participating in a series of academic conferences commemorating the 20th anniversary of the founding of the School of Bioethics at the Universidad Anahuac in Huixquilucan state. The bishops criticized Mexico City's new law at a press conference held on Wednesday.

“What just happened in California is very significant,” Miranda said, referring to a recent federal judge's ruling that overturned the state's gay marriage law, Proposition 8. “On two occasions people spoke out against the legal recognition of gay marriage and twice a judge changed the popular vote with a ruling. In Mexico, I don't know well the mechanism used, but the people were not consulted, there's wasn't a referendum either.”

In December, Mexico City became the first autonomous municipality in Latin America to approve a gay marriage law. The conservative federal government challenged the law, but the nation's Supreme Court declared the law, which, for the first time, also allows gay couples to adopt, constitutional, and ruled that all Mexican states must recognize the gay marriages of the nation's capital.

Both prelates said such unions go against nature, and that gay couples adopting children cannot be considered parenthood “but a substitute that can harm the child, a grave injustice that cannot be described.”