The two most popular shoe brands in America are headed for a showdown in court. Earlier this month, Number one Nike filed a lawsuit against number two Skechers, claiming patent infringement over some of its design patents, according to WWD. The patents, for sneaker soles and uppers, were issued in 2014 and 2015.

In the suit, filed in a federal court in Oregon, Nike alleged that Skechers’ Burst, Flex Appeal, Skech Appeal and Flex Advantage sneaker lines are copies of its Flyknit line. The Flyknit shoes have yarn and fabric uppers that were developed over four years by the company. Nike released the line with a lot of fanfare in 2012, and because the company sponsored the Olympics in London that year, Flyknit styles were broadcasted all over the world. Nike continues to put a lot of marketing effort into selling the Flyknit shoes as game changing, so it’s no surprise that it wants to protect its investment.

The allegedly infringing Skechers shoes are also made of yarn and fabric, and at least one style, the Burst Ellipse is nearly identical to the Flyknit Lunar 3. (The names are also a little too close to be purely coincidental.) According to Law 360, Nike stated in the complaint, “The overall appearance of the designs of the Nike patents and the corresponding designs of Skechers’ infringing shoes are substantially the same. Skechers intended to copy the designs covered by the Nike patents.”

Design patents protect the ornamental or decorative look of an item. The test for determining whether a design patent is infringing has come to be referred to as the “ordinary observer” test, which dates back to an 1871 case. In Gorham v. White, the Supreme Court ruled that “if in the eye of an ordinary observer, giving such attention as a purchaser usually gives, two designs are substantially the same, if the resemblance is such as to deceive such an observer, inducing him to purchase one supposing it to be the other, the first one patented is infringed by the other.” Courts used to also consider whether the allegedly infringing product copied “the novelty” element of the patented item that distinguished it from the “prior art,” but that separate prong—called the point of novelty—was eliminated in 2008 in the Egyptian Goddess v. Swisa decision. The prior art discussion now happens in conjunction with the “ordinary observer” analysis.

This isn’t the first legal fight between the two companies; Converse, a Nike subsidiary, sued Skechers and several other brands for trademark infringement over its popular Chuck Taylor sneakers in 2014. Skechers is also currently the defendant in Adidas’ trademark infringement suit.

If you think someone is infringing on your patent, please contact The Fried Firm.