The Los Angeles County and San Francisco bar associations are among the bar and legal organizations supporting the effort on behalf of same-sex marriage cases before the California Supreme Court, said Elizabeth J. Cabraser of the law firm Lieff Cabraser Heimann & Bernstein.

"Proposition 8 creates the dangerous precedent that the legal and civil rights of minorities, indeed, of any individual or group, could be excised from the California Constitution and the courts would be powerless to reverse such discrimination," Cabraser said.

Backers of the measure maintain it is constitutional and have criticized efforts to overturn the will of voters through the courts.

But Los Angeles County Bar Association President Danette Meyers said the effort involves protecting the rights of minorities.

"The question whether a protected class may be barred from enjoying a fundamental right based on a bare majority vote is a matter of statewide importance," said Meyers. "The implications of the question are wide-reaching; if the majority can relegate disfavored minorities to second class citizenship via the initiative process, no fundamental rights are safe."