The briefs argue that preventing the city from performing same-sex weddings would undermine the system of government. They also contend that nothing in the state constitution requires local officials to obey laws they believe are unconstitutional.
Those are the core arguments in San Francisco's response to efforts by the state attorney general and opponents of same-sex marriage to void nearly 3,600same-sex unions sealed in the last three weeks.
Opponents say the constitution specifically prohibits "administrative agencies" of the state from declaring laws unconstitutional on their own.
Some opponents also plan to argue that marriage in Scandinavia has virtually died as an institution since de-facto same-sex unions became accepted there.
Meanwhile, same-sex couples were dealt a setback in Wisconsin on Friday.
The state Assembly approved a proposed state constitutional amendment banning gay marriages or civil unions. The proposal now goes to the state Senate, and approval there would send the ban to a statewide referendum.
The vote followed an all-night debate, in which opponents slammed the proposal. Supporters largely stayed quiet — refusing to answer questions about the amendment's merits.
Democrats had attempted to derail the amendment through procedural maneuvers.
San Francisco is at the forefront of a nationwide controversy of gay marriages. The furor began when the highest state court in Massachusetts ruled that such marriages are legal, and led President Bush last week to call for a constitutional ban on same-sex marriages.
Since then, the issue has played out on City Hall steps and in legislative chambers across the country.
On Thursday, dozens of same-sex couples sought marriage licenses from the New York City clerk's office but were turned away with a letter explaining that gay marriages are illegal in the state.
New Paltz, N.Y., Mayor Jason West, says he will continue conducting same-sex weddings even though he has been criminally charged, and the mayor of Nyack, John Shields, led a group of same-sex couples to apply for marriage licenses. They were denied.
"If we are denied, we will file a class-action suit against the government for denying us our rights," Shields has said.
A religious rights law firm went to court to bar gay marriages in New York and said it will try to remove West from office. Meanwhile, a gay rights group plans to file a lawsuit in Manhattan seeking full marriage for same-sex couples.
Elsewhere, at least 100 gay couples lined up in Portland, Ore., as Multnomah County handed out licenses for a second day. Democratic Gov. Ted Kulongoski has warned the marriages may not be legal and requested a legal opinion from Oregon's attorney general. Ministers and conservative lawmakers said they would file lawsuit as early as Friday to block the marriages.
Multnomah County officials had issued 422 licenses to gay couples Wednesday.
"This means we finally get to enjoy what every other married couple takes for granted — it means we finally get to enter that world also," said Mary Li, a county employee who was first to get a license.
A group of pastors and conservative lawmakers, dubbed the Defense of Marriage Coalition, announced they would challenge the county's decision in court or a future ballot initiative.
The sister-in-law of Illinois Gov. Rod Blagojevich was arrested Thursday at a pro-gay marriage demonstration in Chicago. Authorities said she charged into a lieutenant and threw him to the ground.
New Mexico Attorney General Patricia Madrid ordered a county clerk to stop issuing marriage licenses to couples of the same sex. The Sandoval County, N.M. clerk's office had granted licenses to 26 same-sex couples last month.
The Kansas House gave tentative approval to a proposed amendment to the state constitution banning gay marriage. The Michigan House will vote next week on a similar measure.
Couples who came to the New York City clerk's office were handed thick letters explaining that local law prohibits gay marriages, based on a ruling a day earlier from the city's top lawyer.
"We're disappointed, but we think it's important for people to come here," said Mara Gottlieb, 33, who was first in line with partner Camille Gonzalez, 38. "We want the politicians to know that this isn't going away."
Mayor Michael Bloomberg has vowed to enforce the law, and state Attorney General Eliot Spitzer also said Wednesday that gay weddings are illegal, though one small-town mayor has conducted gay marriages and another plans to try to obtain licenses.
In New York, the attorney general said current state law prohibits same-sex weddings, but that he would leave it to the courts to decide if the law is constitutional.
"I personally would like to see the law changed but must respect the law as it now stands," Spitzer said in a statement obtained by The Associated Press.
Edward Farrell, the director of the New York Conference of Mayors, said mayors who told him they would have considered performing ceremonies between same-sex couples have changed their mind since Spitzer issued his opinion.
"Part of a mayor's oath of office is to uphold the laws of the state of New York and the attorney general made it clear that same-sex marriages are not authorized under the law," Farrell said.
New York and Oregon are among 12 states without laws explicitly defining marriage as between a man and a woman.
Determined to stop gay marriages, Republican senators in Washington, D.C., said Wednesday they will move later this month to consider several versions of the constitutional amendment to block the same-sex unions.
The legal action against the New Paltz mayor prompted the head of a conservative group to demand that California Attorney General Bill Lockyer file criminal charges against San Francisco Mayor Gavin Newsom.
"He's setting an example of anarchy for the entire nation," said Scott Lively, head of the Pro-Family Law Center. "He does indeed deserve to be arrested for these crimes."