The opinion is here, via Howard. The holding:

We . . . conclude that in view of the substance and significance of the fundamental constitutional right to form a family relationship, the California Constitution properly must be interpreted to guarantee this basic civil right to all Californians, whether gay or heterosexual, and to same-sex couples as well as to opposite-sex couples.

Applying strict scrutiny to the California marriage statute, the court concludes that:

[T]he purpose underlying differential treatment of opposite-sex and same-sex couples embodied in California's current marriage statutes — the interest in retaining the traditional and well-established definition of marriage — cannot properly be viewed as a compelling state interest for purposes of the equal protection clause, or as necessary to serve such an interest. . . . Accordingly, we conclude that to the extent the current California statutory provisions limit marriage to opposite-sex couples, these statutes are unconstitutional.