Gay marriage took another step Tuesday on its march to the U.S. Supreme Court, when a federal appeals court that struck down California's ban on same-sex unions refused to reconsider the ruling.

Now that the case has run its course in the 9th U.S. Circuit Court of Appeals, the measure's sponsors "absolutely" plan to take the case to the high court, said Brian Raum, a lawyer with the Alliance Defense Fund, a Christian legal defense group.

Backers of the ban, known as Proposition 8, now have 90 days to petition the Supreme Court to review the finding that the ban violates the civil rights of gay men and lesbians in California.

If at least four justices agree to accept the case, oral arguments would likely be held next spring.

The developments came after the 9th U.S. Circuit declined to review a February ruling by two of its member judges who found the state's voter-approved same-sex marriage ban was unconstitutional, in part because it rescinded a right that gay and lesbian Californians already had won.