ProtectMarriage.com said it filed a petition to the high court asking it to reverse an appeals court panel that struck down Prop 8.
California voters approved Prop 8, the California Marriage Protection Act, in 2008. It overturned a ruling by the California Supreme Court, which itself had overturned an earlier but similar proposition as unconstitutional.
But a federal judge declared Prop 8 unconstitutional, and three-judge appeals court panel in San Francisco agreed 2-1.
However, the panel stayed its ruling until Prop 8 supporters could ask the full U.S. Court of Appeals for the Ninth Circuit for a new hearing. The full circuit rejected the case, but on June 5 it gave Prop 8 supporters a 90-day stay to file a petition for review at the Supreme Court.
In a statement Tuesday, ProtectMarriage.com said its petition says "our Constitution does not mandate the traditional definition of marriage, but neither does our Constitution condemn it. Rather, it leaves the definition of marriage in the hands of the people, to be resolved through the democratic process in each state."
"The Supreme Court has made it very clear that the age-old definition of marriage as the union of one man and one woman is constitutional as a matter of state public policy," lead counsel Charles J. Cooper with the Cooper & Kirk law firm, said in the statement. "The lower court decisions essentially rejected all relevant Supreme Court and appellate court precedent while attacking the character and judgment of millions of Californians. We are hopeful and confident that the Supreme Court will grant review and ultimately uphold its precedent and the will of the people."