Nearly 380 companies large and small – including a brewery in Maine – signed onto an amicus brief filed Thursday that urges the U.S. Supreme Court to invalidate state bans on same-sex marriage.

The 379 companies, including giants such as The Coca-Cola Co. and Microsoft Corp., make a business case in the brief for why same-sex marriage should be sanctioned nationwide. They argue that the status quo has created a “fractured legal landscape” where employees within the same organization may be treated differently depending on where they live.

“It creates legal uncertainty and imposes unnecessary costs and administrative complexities on employers, and requires differential employer treatment of employees who are similarly situated save for the state where they reside,” says the brief, filed by Washington, D.C.-based law firm Morgan Lewis.

The Supreme Court is scheduled to hear oral arguments April 28 in the case of Obergefell v. Hodges, which will settle the question of whether the Fourteenth Amendment to the U.S. Constitution requires states to grant marriage licenses to same-sex couples and recognize existing same-sex marriages.

Currently, 13 states do not allow same-sex couples to be married.

An amicus brief is filed by someone who is not a party to the case but wants to offer information or an opinion to the court. It is named for the legal term amicus curiae, which means “friend of the court.”

Rising Tide Brewing Co. in Portland signed onto the brief because its owners, Heather and Nathan Sanborn, have been longtime supporters of same-sex marriage rights, Heather Sanborn said.

“It’s something that Nathan and I feel is incredibly important,” she said.

The Sanborns helped raise money for a 2012 referendum effort that resulted in the legalization of same-sex marriage in Maine, becoming acquainted with leaders in the legalization movement in the process, Heather Sanborn said.

Rising Tide was the only Maine-based business that signed onto the brief, although many other companies that do business in Maine also were included. Other companies named in the brief include Procter & Gamble, Amazon.com, Apple, Bank of America, CVS, General Electric and Google.

Sanborn said Rising Tide signed onto a similar brief for the previous same-sex marriage case brought before the Supreme Court, United States v. Windsor. That case led to a 2013 ruling by the high court that the federal Defense of Marriage Act, which allowed states to refuse to recognize same-sex marriages granted in other states, was unconstitutional.

While Sanborn said she was surprised Rising Tide was the only Maine-based company included in the Obergefell v. Hodges brief, she said other businesses operating only in Maine might not have felt the need to get involved because same-sex marriage will remain legal in Maine regardless of the outcome.

“I think we might be one of the smallest companies on the list, but it’s pretty cool,” she said.