Christian Louboutin's vertiginous designs have been spotted on the feet of Oprah Winfrey, Carla Bruni, Renée Zellweger and Beyoncé Knowles. How do we know? Because whenever a starlet takes a step, she reveals a trademark flash of scarlet lacquer on the sole of her shoes.
Louboutin, 47, is now suing French label Yves Saint Laurent, claiming certain models of their Tribute, Palais and Woodstock styles, which are stocked at a number of stores also selling Louboutins, feature a red lacquered sole and are an infringement of his trademark. Louboutin is seeking an injunction against continued sales, as well as more than $1m (£611,000) in damages.
"Defendants' use of a red sole on their infringing footwear threatens to mislead the public, and has impaired plaintiffs' ability to control their reputation," the company complained. Court action follows a letter from executives at Yves Saint Laurent in January, which stated their intention to continue selling the footwear.
Louboutin, whose name has been referenced in songs by everyone from Jennifer Lopez to the Beastie Boys, is keen to protect his signature from those who would like a piece of his high-profile red carpet monopoly.
The label sells more than 500,000 pairs of shoes a year in over 46 countries, with prices ranging from £295 for an espadrille, to several thousand pounds for a bespoke design.
"The cost of enforcing a trademark is high, but if a competitor is infringing on a key area of custom, it's worth it," says Ian Karet, a partner at law firm Linklaters.
Louboutin invented the red sole in 1993 while scrutinising a prototype. "There was this big, black sole," he said, "and then, thank God, there was this girl painting her nails." He used her red nail varnish to cover the rubber sole, thereby inventing one of fashion's most recognisable status symbols. But it took him until 2007 to patent the red sole. "The shiny red colour has no function other than to identify to the public that they are mine," he told a court in his application.
As well as several high street retailers imitating the red soles, last year a 15-year-old entrepreneur in County Kildare set up "Rosso Solini", selling red plastic templates online to stick to soles. "What are we supposed to do?" a Louboutin employee protested. "Call her parents?"
Despite Louboutin creating a website dedicated to eradicating the forgery of his work, policing the use of a specific colour is difficult. "It is possible to copyright a colour," adds Mr Karet, "but it is difficult."