( CNN ) -- Sponsors of the California ballot measure that banned same-sex marriage are seeking to nullify thousands of marriages between gay and lesbian couples performed after the state Supreme Court ruled them constitutional . The passge of Proposition 8 left the future of thousands of marriages between same-sex couples unclear . The sponsors Friday filed responses to three anti-Proposition 8 lawsuits with the state Supreme Court . The briefs also defend Proposition 8 against opponents ' legal challenges , including an argument that the amendment needed a constitutional convention to be added to the state 's constitution . `` We are confident that the will of the voters and Proposition 8 will ultimately be upheld , '' said Andrew Pugno , General Counsel for ProtectMarriage.com and the Proposition 8 Legal Defense Fund . California Attorney General Edmund `` Jerry '' Brown called on the court to reject the initiative . `` Proposition 8 must be invalidated because the amendment process can not be used to extinguish fundamental constitutional rights without compelling justification , '' Brown said in a written statement . Rick Jacobs , founder and chair of the anti-Proposition 8 Courage Campaign , said he was `` appalled '' that the initiative 's supporters wanted to nullify the same-sex marriages that are already on the books . `` The motivation behind this mean-spirited and heart-breaking action should not be allowed to be buried in legal brief , '' he said . `` If Proposition 8 's sponsors plan to destroy lives , they should at least have the courage to admit it publicly . '' Opponents filed suit quickly after the November 4 election in which Proposition 8 passed 52 percent to 48 percent , effectively reversing a California Supreme Court decision that it was unconstitutional to deny marriage licenses to same-sex couples . The vote also prompted a series of protests , some aimed at supporters of the proposition . The proposition , which added an amendment to the state constitution , defined marriage as between one man and one woman . Opponents argue that the amendment can not be applied retroactively , but proponents say the amendment is clear on that issue . `` Proposition 8 's brevity is matched by its clarity , '' one of the briefs read . `` There are no conditional clauses , exceptions , exemptions , or exclusions : 'Only marriage between a man and a woman is valid or recognized in California . ' `` ... Its plain language encompasses both pre-existing and later-created same-sex ( and polygamous ) marriages , whether performed in California or elsewhere . With crystal clarity , it declares that they are not valid or recognized in California . '' Opponents are also seeking to have the amendment nullified , arguing that it alters the state 's constitution -- meaning the state Supreme Court 's May ruling -- and therefore , according to state law , is a revision that requires a constitutional convention . Proponents of the amendment disagree . `` Petitioners ' challenge depends on characterizing Proposition 8 as a radical departure from the fundamental principles of the California Constitution , '' their briefs said. `` ... But that portrayal is wildly wrong . Proposition 8 is limited in nature and effect . It does nothing more than restore the definition of marriage to what it was and always had been under California law before June 16 , 2008 -- and to what the people had repeatedly willed that it be throughout California 's history . '' California voters passed a ballot initiative in 2000 that changed the state 's Family Code to formally define marriage in the state between a man and a woman . After San Francisco Mayor Gavin Newsom performed same-sex marriages in 2004 , which were promptly annulled , Newsom and others sought to have the ballot initiative struck down . The California Supreme Court did so in May , and same-sex marriages were performed legally in California a month later . The court 's ruling said the right to marry is among a set of basic human rights `` so integral to an individual 's liberty and personal autonomy that they may not be eliminated or abrogated by the legislature or by the electorate through the statutory initiative process . '' But opponents had already been at work on Proposition 8 , seeking to enshrine the marriage definition in the constitution , and the initiative was approved for the November 4 vote . Proposition 8 supporters also announced the addition of Kenneth Starr to their legal team . Starr will serve as lead counsel and argue their case to the Supreme Court . Starr , the dean of Pepperdine Law School , investigated the suicide of Clinton deputy White House counsel Vince Foster and the Whitewater affair . The $ 70 million investigation turned up evidence of President Clinton 's affair with Monica Lewinsky and led to Clinton 's impeachment by the House of Representatives . He was acquitted by the Senate .
Ballot initiative 's sponsors have filed several lawsuits with state Supreme Court . One seeks to prevent same - sex marriages occurring when they were legal . Sponsors also respond to lawsuits seeking to block Prop 8 .