The trademark spat between two purveyors of $40 t-shirts branded with the word "Saturday"—Saturdays Surf NYC and Kate Spade Saturday—has been ugly from the get-go. Beyond the courtroom arguments over the word Saturday, allegations of "swagger-jacking" (copying or imitating) and social media defacement have been thrown around.

On Monday, a winner finally emerged in the battle over upscale casual wear. Debevoise & Plimpton persuaded Southern District Judge Miriam Cedarbaum (See Profile) to rule for its client Kate Spade LLC, and to reject Saturdays Surf NYC's trademark infringement claims in a 20-page decision.

The run-up to the ruling was quick and contentious. Following a letter-writing exchange between the two companies' lawyers late last fall, Debevoise filed a complaint in the Southern District asking for a declaratory judgment that Kate Spade Saturday didn't infringe on Saturdays Surf NYC's trademark. The complaint accused Saturdays Surf of planting a fashion blog post headlined "Kate Spade Swagger Jacks Saturdays NYC," which claimed in all caps that "KATE SPADE WILL DO WHATEVER THE FUCK IT WANTS." The complaint also accused Saturdays NYC of defacing the Kate Spade Saturday Instagram and Twitter pages by calling Kate Spade a "fraud," "fakes," and "lazycorporatetools."

In an answer, filed by Saturdays Surf NYC's lawyers at Foley & Lardner, the company denied taking any part in anti-Kate Spade blog or social media campaigns. The answer added counterclaims against Kate Spade, which had announced the launch of its Kate Spade Saturday brand in late 2012. Saturdays Surf NYC, which opened its flagship surfshop in SoHo in August 2009 and started selling ready-to-wear clothing bearing the Saturdays mark in July 2010, accused Kate Spade of trademark infringement, unfair competition, misappropriation of intellectual property rights, and added state law claims of deceptive trade practices and trademark dilution.

Less that a week after the close of a five-day bench trial, Cedarbaum denied all of Saturdays Surf's claims. She found that "Saturday" is a relatively weak mark for apparel and that there's little likelihood that consumers will be confused by the brands. Kate Spade Saturday includes its famous Kate Spade house mark on its products, which are marketed to women, while Saturdays Surf NYC focuses on products for men.

"Overall, the evidence shows that the word 'Saturdays' is commonly used in the context of apparel, and it is not clear that the defendant can monopolize this word alone," Cedarbaum wrote in Kate Spade LLC v. Saturdays Surf, 12 Civ. 9260. The judge also focused on the gender mismatch between the companies' products and marketing. "This results in significant competitive distance between the two lines and makes confusion much more unlikely," the judge wrote.

"The judge clearly understood the distinction between these two brands," David Bernstein of Debevoise, who led the team for Kate Spade, said in an interview. He added, "Kate Spade Saturday is a great mark."

In a statement released Tuesday, Kate Spade Saturday's parent company, Fifth & Pacific Companies Inc., said Cedarbaum's findings "align exactly with what we believe—that both companies and brands can peacefully coexist in the market."

Morgan Collett, cofounder of Saturdays Surf NYC, said in a statement that the company is disappointed in the outcome, and its attorneys are evaluating the decision and whether to appeal.

"Saturdays obviously disagrees with the court's ruling and believes that confusion already exists in the marketplace with all of the similarities between both brands and will only become more of a problem as Kate Spade Saturday increases its advertising presence around the globe," he said. "Saturdays will continue to vigorously protect its signature brand and become an even more significant presence in the fashion world and beyond."

Robert Weisbein at Foley & Lardner, represents Saturdays Surf NYC. He did not immediately return a call for comment.