In a 4-3 ruling, the California Supreme Court ruled Thursday that same-sex couples should be permitted to marry, rejecting state marriage laws as discriminatory. The broadly worded decision is also expected to have the effect of invalidating virtually any law that discriminates on the basis of sexual orientation.
Lesbian talkshow host Ellen DeGeneres announced her plans to wed her long-time partner Australian actress Portia de Rossi during the taping of her talk show on Thursday (to be aired on Friday in the US), the day the California Supreme Court announced its ruling.
Two dozen gay couples along with the city and gay rights organisations then sued.
The turn of events spurred a national dialogue over gay rights and a conservative backlash in a presidential election year which resulted in several states passing constitutional amendments banning gay marriage. Today, 27 states have such amendments.
Chief Justice Ronald George, who wrote the 121-page majority opinion, said the state Constitution's guarantees personal privacy and autonomy which protects "the right of an individual to establish a legally recognised family with the person of one's choice."
He said the 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 opposite-sex couples."
Governor Arnold Schwarzenegger, who previously has vetoed two bills in favour of gay marriage, issued a statement saying he "respects" the decision and "will not support an amendment to the constitution that would overturn" it.
However religious and social conservatives who oppose same-sex marriage said the court had overstepped its bounds and are seeking to override the court ruling in favour of same-sex marriage.
Until that happens, same-sex couples are likely to be able to tie the knot in as little as a month. And unlike Massachusetts - the only other state where same-sex marriage is legal, California has no residency requirement for obtaining a marriage license; meaning gays from around the country are able to go to California to be wed.
Prior to the ruling, California, New Jersey and Vermont have legislation which grants same-sex partners many of the same legal rights as married couples.
The ruling is considered monumental by virtue of the state's size - 38 million of the total population of 302 million are Californian residents. According to U.S. census figures, there are some 100,000 same-sex couples in California, about a quarter of whom have children.
The California Supreme Court was the first state high court to strike down a law barring interracial marriage in a 1948. The United States Supreme Court did not follow suit until 1967.