Christian Louboutin redefined high-fashion footwear with his signature red sole. The shoes with the red soles have inspired pop music singles, museum retrospectives, and even articles in the New Yorker. Fashionistas around the world buy Louboutin’s shoes in droves, despite their prohibitory pricing. And so it came as no surprise when Louboutin took the equally famous and fashionable designer Yves Saint Laurent (YSL) to court in August of 2011 for stealing his look; after all, such a lucrative feature certainly required a level of jealous protection, and everyone who was anyone (in the world of haute couture footwear at least) knew that the red sole was Louboutin’s. What did come as a surprise was the judge’s ruling: it went against Louboutin. Indeed, the court not only denied Louboutin’s motion for a preliminary injunction against the sale of four different pairs of shoes from YSL’s Cruise 2011 collection—it also strongly suggested that Louboutin had no viable claim for trademark infringement in the first place. In concluding that Louboutin’s registered mark—known as the “Red Sole Mark”—should be invalidated, the court relied upon the complex and ill-defined doctrine of aesthetic functionality. Under this doctrine, a design feature merits trademark protection only if it can be shown to perform no significant function other than acting “as a symbol that distinguishes a firm’s goods and identifies their source.” The aesthetic functionality doctrine figures in trademark law as a sort of gatekeeper—its application is meant to advance competition in the United States marketplace by preventing any one entity from claiming exclusive ownership over design features that impact the cost, use, or purpose of commercial items. Though this policy goal is easy enough to recognize as legitimate, the conceptual and practical realities of the doctrine are much more convoluted. With the recent, widely publicized decision in the Louboutin case, however, the time has come to deconstruct the aesthetic functionality problem. This Comment explores the aesthetic functionality doctrine, using the Louboutin case and the world of high-fashion footwear to illuminate the present legal and conceptual difficulties with its application. It provides an overview of the two legal arenas implicated by the Louboutin case and necessary to an understanding of the aesthetic functionality doctrine—the trademarking of color and the historical approaches to the functionality doctrine. It then analyzes the current state of the law on aesthetic functionality, examining Supreme Court and circuit court precedent, and also closely reading the reasoning of the district court and the Second Circuit in the Louboutin case. Examining this law through the lens of the high fashion industry, this Comment suggests that there are two plausible formulations of aesthetic functionality, one of which supports the district court’s holding in Louboutin where the other seems to contradict it. This Comment argues that the aesthetic functionality formulation ultimately adopted by the federal courts will have serious repercussions for the concept of secondary meaning, and concludes that the superior formulation of aesthetic functionality would allow Louboutin to maintain his Red Sole Mark, giving fashionistas the opportunity to run their red soles to venues other than the courtroom.