The groups Wednesday filed a writ of petition with the state supreme court challenging Proposition 8 as being an improper use of a ballot initiative to strip homosexuals of a fundamental constitutional right.

"A major purpose of the constitution is to protect minorities from majorities. Because changing that principle is a fundamental change to the organizing principles of the constitution itself, only the Legislature can initiate such revisions to the constitution," ACLU attorney Elizabeth Gill said in a written statement issued by the ACLU, Lambda Legal and the National Center for Lesbian Rights.

A similar writ was filed before the election on the grounds Prop 8 should not have been on the ballot and was rejected without comment. The ACLU said the rejection did not prohibit them from trying again.

Prop 8 was put on the ballot in response to a state Supreme Court ruling earlier this year that declared same-sex marriages to be legal. The measure was considered passed by a narrow margin Wednesday, although the official opposition group said it would not concede until the absentee ballots were counted.

Meanwhile, Prop 8 proponents declared that marriage in California was once again reserved solely for heterosexual couples although civil unions for homosexuals were still legal.