With a one-vote majority, California's Supreme Court overturned a law banning same-sex marriage yesterday (PDF of decision). The case is a consolidation of appeals to the same court's ruling in 2004 that San Francisco had illegally granted marriage licenses to same sex couples. In that decision they had expressly stated that they were not ruling on the constitutionality of the law, but only one whether or not the law had been broken. In this case they examine the constitutionality of the law and find that the law violates basic constitutional rights: the right to form a legally recognized family with a partner one loves, and the right to equal protection under the law.
The CA decision refers back to a much earlier decision - Perez v. Sharp in 1948 - in which the court found that laws banning interracial marriage were unconstitutional. This was 19 years before Loving v. Virginia, the U. S. Supreme Court case that did the same thing nationwide. (Mildred Loving, whose marriage to Richard Loving was at the center of that case, died on May 2.)
Kenji Yoshino, a Yale Law professor writing for Slate today, points out that one strength of yesterday's decision is that it is based not only on liberty (the right to form marriages based on love and choice) but also on equality (the right to be treated equally by the law regardless of sexual orientation), and points out that because of that, this decision goes beyond the right to marry and makes it clear that any California law that discriminates against people based on sexual orientation is equally in trouble. That's the good news.