SAN FRANCISCO —  The California Supreme Court (search) plans to hear oral arguments May 25 on whether San Francisco's mayor had the authority to issue same-sex marriage licenses.

The seven-member court said Wednesday it would devote two hours to the arguments. Under court rules, the justices then must rule within 90 days.

The cases brought by Attorney General Bill Lockyer (search) and the conservative Alliance Defense Fund focus almost exclusively on whether Mayor Gavin Newsom (search) could issue same-sex marriage licenses by unilaterally declaring that such marriages should be lawful.

California law defines marriage as a union between a man and woman.

The high court stopped gay marriages (search) at San Francisco's City Hall last month after 4,000 gays were wed, pending the outcome of the legal challenges.

Lockyer and the conservative group said upholding Newsom's actions would allow other government officials to subvert other laws.

The justices this month asked the parties whether they should nullify the roughly 4,000 marriages if they side against Newsom.

Lockyer has taken no position on gay marriage, but told the justices the marriages should be invalidated because Newsom overstepped his authority.

The Arizona-based Alliance Defense Fund agreed with Lockyer, but also disapproves of gay marriage.

For his part, Newsom said his interpretation of the California Constitution demanded that he issue the licenses.