Gay couple Adrian Genesi, 50, (L) and James Davis, 44, kiss after feeding each other wedding cake as they celebrate their one-year wedding anniversary in West Hollywood, California, June 16, 2009. The couple were married when same-sex marriages were first allowed last year. [Agencies]

"Their presence in California serves to show that married gay couples don't cause any problems," said Jennifer Pizer, director of the marriage project at Lambda Legal, which argued against Proposition 8 before the California Supreme Court.

Louise Brooks, spokeswoman for California Faith for Equality, said organizers want to celebrate last year's milestone in gay rights while renewing calls to push for continued same-sex marriage rights.

She said the events, designed to be more like vigils than parties, are "a remembrance of what we once had but don't have anymore."

Adrian Genesi, 50, (L) feeds his spouse James Davis, 44, wedding cake as they celebrate their one-year wedding anniversary in West Hollywood, California, June 16, 2009. [Agencies]

Earlier this month, New Hampshire became the sixth US state to legalize gay marriage, following Massachusetts, Connecticut, Maine, Vermont and Iowa. Opponents hope to overturn Maine's law with a public vote.