A disappointed co-op buyer can proceed with his complaint that a Long Island cooperative discriminates against single men, a federal judge has ruled.

Jeffrey M. Lax contends that 29 Woodmere Boulevard Owners Inc. and related parties rejected his application to buy an apartment for $200,000 because they had developed a jaundiced attitude toward single men after a previous owner who was male and unmarried threw loud parties and smoked marijuana.

Seeking unspecified damages, Mr. Lax argues the Fair Housing Act outlaws “sex plus” discrimination based on his gender and another factor—here his marital status.

The co-op pressed for dismissal of Mr. Lax’s suit, arguing among other things, that his discrimination claim was not cognizable under the statute.

But Eastern District Judge Joseph F. Bianco, sitting in Central Islip, disagreed and allowed the case to move to discovery before Magistrate Judge William D. Wall.

Noting he was procedurally bound at the dismissal stage to accept Mr. Lax’s allegations as true, Judge Bianco wrote in Lax v. 29 Woodmere Boulevard Owners, 10-cv-4008, that “plaintiff has asserted a plausible ‘sex plus’ housing discrimination claim against the Board and Co-op, as well as against [Steven] Mirsky and [managing agent Alexander Wolf & Company], who can be held liable for discriminatory conduct in which they participated.”

Judge Bianco ruled for the first time that the “sex plus” discrimination claim—typically used in the employment bias context—applies in housing cases, said Mr. Lax’s attorney, M. Todd Parker of Moskowitz & Book.

In April 2010, Mr. Lax, a professor who chairs the business department at Kingsborough Community College, executed a contract to buy unit 4J from the previous residents, Martin and Sylvia Berkowitz, for $200,000 in cash. Mr. Lax dealt with the couple’s son, Murray, who acted as their agent. The couple now live in a Massachusetts assisted-living home.

Before Mr. Lax made his offer, the unit was listed at $219,000.

Despite the contract’s execution, the co-op board still had to approve the sale. The board asked Mr. Lux for reference letters, pay stubs, income tax returns for the past two years and information about prospective assets and liabilities—all of which Mr. Lax provided.

Steven Mirsky, a vice president of the co-op’s managing agent, Alexander Wolf & Company, told Mr. Lax his application was denied. Mr. Lax’s request for reconsideration was also denied.

Mr. Berkowitz later told Mr. Lax the reason for the board’s decision was that the sales price was too low. Mr. Lax indicated he was open to paying more. But in a subsequent July e-mail, Mr. Berkowitz said the co-op board would refuse no matter the sales price.

Meanwhile, by June, Mr. Lax had learned from an unnamed resident that the board engaged in “a pattern” of discriminatory conduct against single men, owing to its experience with the unruly resident.

When Mr. Lax received Mr. Berkowitz’s e-mail on the board’s outright refusal, he contacted Alexander Wolf & Company and complained.

In an Aug. 28 letter, the board insisted the denial was based on the purchase price and did not address Mr. Lax’s question about the board’s refusal in light of his willingness to pay more.

Around that time, the unit was listed for $200,000.

Mr. Lax filed suit on Sept. 1, 2010, naming the co-op, its board members and managing agent as defendants.

Mr. Lax initially named the Berkowitzs but voluntarily dismissed those claims in September.

In court papers, the co-op defendants maintained marital status was not protected by the Fair Housing Act as a matter of law. Furthermore, Mr. Lax did not plead sufficient facts that defendants conspired against him because of his gender and marital status, they said.

But Judge Bianco said case law had already deemed Mr. Lax’s claimed class combining gender and marital status as protected.

“Although none of these cases were in the context of the [Fair Housing Act], the court finds that the Supreme Court and Second Circuit jurisprudence on ‘sex plus’ claims under other discrimination statutes applies with equal force to the language of the [Fair Housing Act],” he wrote.

In a footnote, he added that the defendants’ arguments against the court’s reliance on Title VII cases to interpret the Fair Housing Act were “clearly incorrect” because other courts, like the Second Circuit, have already done so.

As far as the facial sufficiency of the complaint, Judge Bianco said a three-part analysis put forward by defendant was not applicable in the dismissal stage because all that was required was a “short and plain statement of the claim.”

The co-op defendants also contended that Mr. Lax’s suit was defective because it did not show similarly situated women were treated differently. Judge Bianco, however, said such proof was not a “prerequisite” to a housing discrimination claim.

He also decided to keep the managing agent and Mr. Mirsky in the suit, although they were agents of the co-op.

The judge said Mr. Lax adequately showed “Mirsky and Wolf were involved in the decision-making process regarding the sale of apartments.”

Judge Bianco denied Mr. Lax’s motion for sanctions.

Mr. Parker wrote in an e-mail that “this is a very important decision because it recognizes for the first time that sex plus claims are cognizable under the Fair Housing Act. Judge Bianco’s application of the reasoning found in Title VII sex plus cases is exactly right and finds ample support in Supreme Court and Second Circuit jurisprudence on this issue.”

David A. Boyar of D’Amato & Lynch represents the Woodmere defendants. He did not respond to a request for comment.

Andrew E. Curto of Forchelli, Curto, Deegan, Schwartz, Mineo, Cohn & Terrana in Mineola represented the Berkowitzs and was assisted by Danielle Gatto.

He called their exit from the case “a just result” but noted “my clients spent a lot of money getting out of an action they never should have been in in the first place.”

With their life savings tied up in the unit, Mr. Curto said it would make no sense for his clients to have conspired against Mr. Lax.

The two-bedroom, two-bath unit, still unsold, is listed online for $200,000.