LONDON — Can you trademark a color?

The French shoe designer Christian Louboutin — known for sky-high stiletto shoes with scarlet soles that can sell for upward of $1,000 — has been trying to do so for years. Mr. Louboutin first grabbed his assistant’s red nail polish and applied it to the outsoles of a shoe a quarter-century ago. Since then, he has frequently declared the design element to be his recognizable signature, and argued it merits legal protection.

On Tuesday, the European Union’s highest court dealt a blow to that effort.

Mr. Louboutin had filed a lawsuit in 2012 against Van Haren, a Dutch company whose retail outlets were selling affordably priced high-heeled women’s shoes with red soles. Lawyers for Mr. Louboutin claimed that the shoes sold by Van Haren, part of its Fifth Avenue by Halle Berry line, infringed on his brand’s trademark for footwear. That trademark, registered in Belgium, the Netherlands and Luxembourg, referred to “the color red (Pantone 18 1663TP) applied to the sole of a shoe.”

Van Haren had to temporarily stop making and selling the line of shoes, but the company’s lawyers fought back and the case eventually made its way to the European Court of Justice.

They have now won something of a reprieve. Maciej Szpunar, an advocate general for the court, said on Tuesday that Mr. Louboutin’s red soles were not a separate entity from the shape of his high-heeled shoes, and shapes typically cannot be trademarked under European Union law.