In a 172-page opinion, the seven-member court ruled there is no California law limiting marriage to a man and woman.

The court likened bans on same-sex marriages to interracial marriage bans, which have been determined unconstitutional.

"In contrast to earlier times, our state now recognizes that an individual's capacity to establish a loving and long-term committed relationship with another person and responsibly to care for and raise children does not depend upon the individual's sexual orientation …," Chief Justice Ronald M. George said in writing for the majority.

"We therefore 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 ..."

In his concurring and dissenting opinion, Justice Marvin R. Baxter said the decision goes too far.

"Nothing in our Constitution, express or implicit, compels the majority's startling conclusion that the age-old understanding of marriage -- an understanding recently confirmed by an initiative law -- is no longer valid," Baxter wrote.

The ruling stemmed from six cases that were consolidated before the court.