In a decision of 5 September 2012, the 2nd US Circuit Court of Appeals in New York ruled that the red soles used in Christian Louboutin’s shoes were a "distinctive symbol that qualifies for trade mark protection" and therefore a valid and enforceable trademark. As background to the case, Louboutin had seen red and sued rival fashion house Yves Saint Laurent (YSL) in 2011 after YSL launched a pair of shoes with a red sole, which Louboutin is arguably famous for. In the initial decision in the US District Court for the Southern District of New York, the judge denied the motion for an injunction and stated that Louboutin’s trade mark was "likely not enforceable". On appeal, the Circuit Court found that the District Court’s decision was inconsistent with a Supreme Court Judgement in Qualitex Co. v Jacobson Products Co. 514 U.S. 159, 162 (1995) and that the previous court was incorrect because Louboutin’s red soles have the requisite "distinctiveness" to merit trade mark protection.

The Circuit Court concluded that the trade mark, which consists of a red, lacquered outsole had acquired "secondary meaning" as a distinctive symbol that identifies the Louboutin brand, but limited the trade mark to use where the outsole contrasts with colour of the rest of the shoe. This detail means that YSL can still use its red sole as part of a monochrome red shoe. Some observers believe that the judgment shows that it is possible to trademark a colour through consistent and prominent use.

The US judgment is not legally binding outside the US, but it highlights a risk for advertisers who may wish to use such items in their advertisements, especially where these may run online. Advertisers should be careful when using any such distinctive products over which exclusive usage rights may be claimed.