Backers of California’s Proposition 8 followed through on their intention to seek a Supreme Court review of lower court rulings overturning the state’s ban on same-sex marriage.

In a petition filed with the high court on Tuesday, attorneys for the supporters of the Proposition wrote that the central question in the case is “where the Equal Protection Clause of the Fourteenth Amendment prohibits the state of California from defining marriage as the union of a man and a woman.”

Earlier this year, the 9th Circuit Court of Appeals ruled in favor of the plaintiffs in the case and refused to overturn a district court ruling declaring Proposition 8 unconstitutional. But the appellate opinion was on somewhat narrower grounds, citing the 1996 decision in Romer vs. Evans as precedent. That decision invalidated a Colorado ballot initiative that limited the rights of gays and lesbians.

“The age-old definition of marriage as the union of one man and one woman is constitutional as a matter of state public policy,” ProtectMarriage, the org that led the effort to pass Prop 8, said in a statement. “We are hopeful and confident that the Supreme Court will grant review and ultimately uphold its precedent and the will of the people.”

The full petition is here.

The Supreme Court also will be considering other cases challenging the constitutionality of the Defense of Marriage Act, which a handful of courts have found unconstitutional.

The American Foundation for Equal Rights, which is leading the legal effort to overturn Prop 8, plans to oppose the petition.

In a statement, one of their attorneys, Theodore Boutrous, said, “Because two federal courts have already concluded that Proposition 8 is unconstitutional, gay and lesbian Californians should not have to wait any longer to marry the person they love.  We therefore will oppose the petition for a writ of certiorari.  However, we recognize that this case presents constitutional issues of national significance, and are ready to defend our victories before the Supreme Court.”