California's Supreme Court declared gay couples in the nation's biggest state can marry — a monumental but perhaps short-lived victory for the gay rights movement Thursday that was greeted with tears, hugs, kisses and at least one instant proposal of matrimony.

John Lewis, right, hugs his partner, Stuart Gaffney, left, outside of the California State Supreme Court building in San Francisco, Thursday, May 15, 2008, after the California Supreme Court overturned a voter-approved ban on gay marriage in a ruling that allows same-sex couples in the nation's biggest state to tie the knot. Gaffney and Lewis are one of the main plaintiffs in the case.

Same-sex couples could tie the knot in as little as a month. But the window could close soon after — religious and social conservatives are pressing to put a constitutional amendment on the ballot in November that would undo the Supreme Court ruling and ban gay marriage.

"Essentially, this boils down to love. We love each other. We now have equal rights under the law," declared a jubilant Robin Tyler, a plaintiff in the case along with her partner. She added: "We're going to get married. No Tupperware, please."

A crowd of people raised their fists in triumph inside City Hall, and people wrapped themselves in the rainbow-colored gay-pride flag outside the courthouse. In the Castro, the historic center of the gay community in San Francisco, Tim Oviatt wept as he watched the news on TV.

"I've been waiting for this all my life. This is a life-affirming moment," he said.

By the afternoon, gay and lesbian couples had already started lining up at San Francisco City Hall to make appointments to get marriage licenses.

In its 4-3 ruling, the Republican-dominated high court struck down state laws against same-sex marriage and said domestic partnerships that provide many of the rights and benefits of matrimony are not enough.