(San Francisco, California) The California Supreme Court will hear oral arguments in the challenges to Proposition 8 on March 5.

The arguments will be made before the same 9-member court that first legalized gay marriages last spring. Some 18,000 same-sex marriages were conducted between June and election day.

Following passage of the proposition, the American Civil Liberties Union, Lambda Legal and the National Center for Lesbian Rights filed lawsuits challenging the constitutionality of the vote.  They were joined by additional suits by the cities of San Francisco and Los Angeles.

The lawsuits charge that Proposition 8 is invalid because the initiative process was improperly used in an attempt to undo the constitution’s core commitment to equality for everyone, by eliminating a fundamental right from just one group – lesbian and gay Californians.

They also say that Proposition 8 improperly attempts to prevent the courts from exercising their essential constitutional role of protecting the equal protection rights of minorities. The suits say that under the California Constitution, such radical changes to the organizing principles of state government cannot be made by simple majority vote through the initiative process, but instead must, at a minimum, go through the state legislature first.

The California Constitution itself sets out two ways to alter the document that sets the most basic rules about how state government works, the groups said in a written brief to the court.

Through the initiative process, voters can make relatively small changes to the constitution.  But any measure that would change the underlying principles of the constitution must first be approved by the legislature before being submitted to the voters.  That didn’t happen with Proposition 8, and that’s why it’s invalid, the petitioners said.

California Attorney General Jerry Brown is also asking the Court to invalidate Proposition 8 on the ground that certain fundamental rights, including the right to marry, are inalienable and can not be put up for a popular vote.

In a brief submitted to the court Friday, Brown’s office said the measure should be invalidated because it deprives people of the right to marry—an aspect of liberty that the Supreme Court has concluded is guaranteed by the California Constitution.

“Proposition 8 must be invalidated because the amendment process cannot be used to extinguish fundamental constitutional rights without compelling justification,” Brown’s brief said.

Brown argued that in order to invalidate such a fundamental right, the Court “must determine that there is a compelling justification to do so.” But in the marriage cases that the court ruled on earlier this year, striking down the ban on gay marriage “the court found that no such compelling justification exists. Accordingly, Proposition 8 must be stricken,” the brief said.

Moderate denominations, labor and legal groups also have submitted written briefs to the court calling for the proposition to be dropped.

On the other side, Protect Marriage Coalition, the umbrella group that put Prop 8 on the ballot, argues in its brief to the court that the will of the people must be respected by the court and that the measure also invalidated those marriages performed prior to the vote.

The coalition has hired Ken Starr who led the inquiry into President Bill Clinton’s affair with Monica L. Lewinsky, to argue its case before the high court.

The Supreme Court justices will have to determine three main issues: Is Prop 8 invalid because it constitutes a revision of, rather than an amendment to, the California Constitution; Does it violate the separation of powers doctrine under the California Constitution; and if it is legal, what is the status of the 18,000 marriages that were performed last year.

After the court hears the legal arguments it will be several months before a decision is issued.