(San Francisco, California) The California Supreme Court will hear oral arguments on Thursday challenging Proposition 8, the measure passed by voters in November that bars same-sex marriage.

Prop 8 was passed by voters by a slim 52 percent. The American Civil Liberties Union, Lambda Legal and the National Center for Lesbian Rights immediately filed lawsuits challenging the constitutionality of the vote.  They were joined by additional suits by the cities of San Francisco and Los Angeles and a legal opinion by California Attorney General Jerry Brown.

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.

Brown’s office took a slightly different approach, arguing in its brief to the court that Proposition 8 should be invalidated on the ground that certain fundamental rights, including the right to marry, are inalienable and cannot be put up for a popular vote.

The brief said said the measure should be overturned 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.

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.

Wednesday night same-sex couples and their supporters will hold candlelight vigils in at least 15 cities across the California. Among the major cities are San Francisco, Los Angeles, San Diego and Palm Springs. The vigils are being hosted by Marriage Equality, Equality California and local LGBT rights groups.

The issue of same-sex marriage in California dates back to 2004 when San Francisco mayor Gavin Newsom began issuing marriage licenses to same-sex couples.  Some 8,000 couples exchanged vows before the state Supreme Court ruled Newsom had acted illegally.

The court nullified the marriages but said its ruling dealt only with Newsom’s actions.  The justices said at the time the question of whether barring same-sex couples from marrying violated the state’s equal protection clause of its constitution was a separate matter.

Legal challenges on the constitutional question were begun almost immediately. Three separate suits ultimately were wrapped together into a single case.

In March 2005 a Superior Court judge in San Francisco ruled that the law denying same-sex marriage was unconstitutional but the ruling was stayed while the state appealed.

In October, 2006, the California Court of Appeal in a split decision overturned Kramer’s ruling.

Last May the state Supreme Court upheld the appeal court ruling and some 18,000 same-sex couples were married before Prop 8 was approved in November.