Louboutin vs. Yves Saint Laurent

The bright-red lacquered sole of a Christian Louboutin shoe serves a lofty purpose. The flash of the red sole, on a runway or daintily emerging from a limousine, broadcasts "chic" to every fashion hound within eyeshot. Devotees include actor Sarah Jessica Parker, Gossip Girl's Blake Lively, and Jennifer Lopez, who released a song in 2009 titled "Louboutins." It is simply impossible to be unfashionable while wearing a pair of Louboutins.

This exclusiveness - and the desire to hold onto it - is at the heart of the million-dollar lawsuit that Louboutin brought in April 2011 against rival fashion house Yves Saint Laurent.

Louboutin accused YSL of copying his trademarked red-soled shoes. The offending models included four shoe designs from YSL's Cruise 2011 collection: the Tribute, Tribtoo, Palais, and Woodstock, all of which have red soles. YSL filed a counterclaim seeking cancellation of Louboutin's trademark.

It's easy to look at the footwear fight, which occupied every fashion headline last week, as a color war. But with approximately 240,000 pairs of Louboutins sold each year in the United States, the issue goes deeper than just copyright infringement. The red sole represents profit. Projected 2011 revenue for Louboutin is $135 million, with a pair of shoes selling for $600 and up - way up. When U.S. District Judge Victor Marrero, sitting in Manhattan, ruled in favor of YSL on the trademark issue last week, it opened the door for other designers to make and sell red-soled shoes. Think high fashion at Payless prices.

Louboutin is challenging Marrero's ruling. Both parties are scheduled to return to court Wednesday.

 The red Louboutin sole is as recognizable as Tiffany blue or Burberry plaid - both of which are also trademarked to protect against unauthorized copying.

In today's world, successful designers are used to piracy. "Knock-offs are a price of entry into the fashion industry," said Corey Field, president of the Copyright Association of the U.S.A. (New York) and an attorney at Ballard Spahr.

Companies such as Burberry and Tiffany use their trademarked colors and patterns as brand identifiers. Under the law, color can serve as a trademark, but only if it distinguishes a brand without serving another function.

Unfortunately for Louboutin, a shoe must have a bottom, and a sole serves a vital function for a shoe.

Whatever the outcome, Field says, consumers will likely still perceive the original red sole as precious: "There will always be a difference between Louboutins and K-Mart pumps."