Flanked by congressional members, Sen. Senator Jeffrey Merkley speaks during a news conference on LGBT discrimination on July 23, 2015.

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WASHINGTON — On Tuesday night, 128 members of Congress weighed in to urge a federal appeals court to protect against sexual orientation-based discrimination under existing civil rights laws.

The request came in an amicus curiae — friend of the court — brief filed in Matthew Christiansen's case before the 2nd Circuit Court of Appeals. Christiansen sued Omnicom Group, Inc. claiming that the company discriminated against him, among other reasons, because he was gay.

Christiansen argued that such treatment should be a violation of the ban on sex discrimination found in Title VII of the Civil Rights Act of 1964, but the trial court judge dismissed the claim because, she wrote, a prior decision of the appeals court — Simonton v. Runyon — prevented her from being able to take Christiansen's position.

Christiansen has now appealed, and Tuesday was the deadline for parties wishing to file amicus briefs on his behalf.

"Now before this Court is the opportunity to rectify a years-long error in Title VII interpretation in the Second Circuit. The solution is straightforward, logical, just and supported by Amici," the brief for the members of Congress urges. "This Court should recognize that 'sex' under Title VII encompasses sexual orientation, and Simonton and any other case law to the contrary should be overturned."

The 105 members of the House and 23 senators are represented by attorney Peter Barbur of Cravath, Swaine & Moore LLP. The brief notes that all signers are co-sponsors of the Equality Act, legislation in Congress aimed at providing explicit protections in federal law against sexual orientation-based and gender identity-based discrimination.

Among other filings was one by the Equal Employment Opportunity Commission, which previously weighed in with a similar brief in a case pending in another appeals court. It had, as an independent agency reached the conclusion that sexual orientation-based discrimination is covered under Title VII a little less than a year ago.

Addressing prior cases in which courts had found Title VII not to protect against sexual orientation discrimination, the EEOC put it bluntly: "The rule that Title VII does not prohibit discrimination based on sexual orientation is outdated."

Specifically, the independent agency's lawyers wrote, "When Simonton was decided in 2000, for example, Bowers [v. Hardwick], which upheld state legislation criminalizing private homosexual conduct, was the law of the land."

The Bowers decision was reversed by the Supreme Court in 2003, the lawyers note, and the high court moved even further after that with the cases striking down the Defense of Marriage Act and ending state bans on same-sex couples' marriages.

LGBT advocates — including the ACLU, Lambda Legal, and National Center for Lesbian Rights — also weighed in with briefs supporting Christiansen.

The Justice Department had not weighed in previously on whether it holds the view that sexual orientation-based discrimination should be covered under Title VII, and, as the midnight filing deadline passed in Christiansen's case, it appeared that the Obama administration will not do so here either.