The lawsuits claimed that revoking the right of same-sex couples to marry is a constitutional "revision" rather than an "amendment". In California, both constitutional "amendments" and "revisions" require that a majority of voters approve the ballot initiative. However, a "revision", defined as a "substantial alteration of the entire constitution rather than to a less extensive change in one or more of its provisions," also requires the prior approval of 2/3 of each house of the California State Legislature. Erwin Chemerinsky, the dean of the law school at the University of California, Irvine, stated, "the California Supreme Court has never articulated criteria for what makes something an amendment versus a revision. So I don't think you can predict anything because there is so little law." Claims made on similar grounds with respect to other constitutional changes have in some cases taken years to be adjudicated, and almost all have failed. Kenji Yoshino, an openly gay man who serves as the Chief Justice Earl Warren Professor of Constitutional Law at New York University School of Law, cast doubt on the "revision" argument, stating that "for both precedential and political reasons, I think this case is a loser." Like the United States Constitution, the California Constitution employs the concept of separation of powers. The lawsuits argue that the protection of minority groups via the Constitution and the Bill of Rights is inherently a judiciary function, which cannot be overturned by the legislative branch of government, and therefore cannot be overturned by the initiative-amendment process. A pending legal issue was whether the approximately 18,000 same-sex marriages already in effect would be retroactively annulled by the constitutional change or whether they would be preserved, since the amendment does not state explicitly that it would nullify same-sex marriages performed before the change took effect. California Attorney General Jerry Brown said that existing same-sex marriages would be unaffected, but other legal experts were uncertain. On December 19, 2008, supporters of Prop. 8 filed briefs responding to each of the anti-Prop. 8 lawsuits already filed with the State Supreme Court and seeking to nullify same-sex marriages already in effect. The Attorney General's response to the lawsuits included a new argument that the Court should overturn Proposition 8. That brief contends that California's initiative-amendment process does not give voters the right to overturn rights in California's Declaration of Rights without a "compelling justification". Plaintiffs in the three lawsuits included same-sex couples who had married or planned to marry, represented by the same legal team that argued and won In re Marriage Cases, Lambda Legal, the National Center for Lesbian Rights, and the ACLU of Northern California, as well as the cities of San Francisco and Los Angeles, and the county of Santa Clara.