Alliance Defense Fund lawyer Brian Raum said Proposition 8 backers "absolutely" would take the case to the high court now that it has run its course at the 9th U.S. Circuit Court of Appeals.
Raum said he expected to get a ruling from the Supreme Court sometime in the fall on whether it would take the case. He did not know if the Proposition 8 defense team would take the entire 90 days they have to petition the Supreme Court.
The move follows a federal appeals court's refusal to revisit a decision by two of its member judges declaring the voter-approved ban to be a violation of the civil rights of gays and lesbians in California.
Backers of the ban petitioned the full 9th U.S. Circuit Court of Appeals in February to review the decision instead of appealing directly to the U.S. Supreme Court.
Gay marriage opponents said at the time they would go to the high court if the appeals court declined to rehear the case.
Same sex unions were briefly legal in California before voters passed Proposition 8 in November 2008. Due to the ongoing legal wrangling, it's unlikely the practice will resume in the state anytime soon.
The 9th Circuit said Tuesday a majority of its 26 actively serving judges had voted not to revisit a three-judge panel's 2-1 decision declaring the voter-approved ban to be a violation of the civil rights of gays and lesbians in California.
The 9th Circuit does not often agree to rehear cases, a procedure known as en banc review. Federal court rules reserve the practice for appeals that involve "a question of exceptional importance" or if the original decision appears to conflict with Supreme Court or 9th Circuit precedents.
After voters approved Proposition 8, two unmarried couples sued to overturn the ban in May 2009, and their lawsuit gave rise the next year to the first federal trial to examine if states can prohibit gays from getting married without violating the constitutional guarantee of equality. U.S. District Judge Vaughn Walker ultimately sided with the couples.
The ban's sponsors appealed, and the split 9th Circuit panel affirmed Walker's finding that Proposition 8 violated those civil rights. But, instead of finding any gay marriage ban would be unconstitutional, the panel limited its decision to California, saying Proposition 8 improperly took away an existing right.
Several other high-profile same-sex cases also are making their way toward the high court. A three-judge panel of the Boston-based 1st U.S. Circuit Court of Appeals declared last week that the federal law that prohibits recognition of same-sex couples unconstitutionally denies Social Security and other federal spousal benefits to married gay couples.