We have previously blogged about the battle over Christian Louboutin’s (“Louboutin’s”) trademark registration for lacquered red soled shoes that is taking place in New York and is now before the Second Circuit. Friends of the Court (the Latin meaning of the phrase amici curiae) that have weighed in on Louboutin’s side include both Tiffany & Co. and The International Trademark Association (“INTA”). Now friends weigh in on behalf of Yves Saint Laurent (“YSL”).

By way of background, Louboutin urged the Second Circuit to reverse the District Court’s order denying it a preliminary injunction on the grounds that Louboutin could not demonstrate that it was likely to succeed on its trademark infringement and unfair competition claims. In support of Louboutin and a reversal, Tiffany & Co. argued that the District Court's opinion in this case had “adopted a sweeping and unprecedented per se rule against granting trademark protection to any single color that is used on any ‘fashion item,’ even where the color has achieved ‘secondary meaning’ and is associated with a single brand.” INTA also weighed in alleging that the color red on soles of shoes was not aesthetically functional and that if left to stand the decision would “upend key aspects of trademark and unfair competition law, making it easier for third parties to use the brands of others.”