The exclusiveness of Christian Louboutin’s red soles is at the heart of a million-dollar lawsuit that Louboutin brought against rival fashion house Yves St. Laurent. Louboutin accused YSL of copying his trademark soles on four shoe designs in the 2011 Cruise Collection. YSL filed a counterclaim seeking cancellation of Louboutin’s trademark.

“Knock-offs are a price of entry into the fashion industry,” said Ballard Spahr of counsel Corey Field, president of the Copyright Association of the U.S.A., adding that color can serve as a trademark, but only if it distinguishes a brand without serving another function.