The United States Conference of Mayors has joined a legal brief urging the Supreme Court to strike down the Defense of Marriage Act (DOMA), which prevents the federal government from recognizing the legal marriages of gay and lesbian couples.

The U.S. Conference of Mayors, which includes 1,309 member cities, each of which is represented by their mayor or other chief elected official, joined nearly 300 companies, as well as individual mayors and trade associations, in an amicus brief filed before the Supreme Court in the case Windsor v. United States.

In the brief, signers called on the high court to strike down the law first enacted in 1996, focusing on how DOMA burdens employers. DOMA “forces us to treat one class of our lawfully married employees differently than another, when our success depends upon the welfare and morale of all employees.”

“Uniting with businesses from Adobe to Xerox in standing against DOMA, the U.S. Conference of Mayors has shown the true American spirit of equality and fairness today,” Evan Wolfson, president and founder of Freedom to Marry, said in a statement. “Mayors know well that marriage and family are the cornerstone of strong communities, and that a federal law that discriminates against marriages violates the Constitution and has got to go.”

Philadelphia Mayor Michael A. Nutter, president of the U.S. Conference of Mayors, is an active member of Mayors for the Freedom to Marry, a group of 300 mayors who have pledged to support efforts to legalize marriage equality in their states.

“The U.S. Conference of Mayors is proud to sign on to this brief,” Nutter said. “Mayors want their citizens and businesses to prosper, and that means supporting them against discrimination – from any level of government. Married means married, and mayors and businesses agree that DOMA can't stand.”