It seems the legal drama surrounding Nike and Adidas’ knitted technology will never end.

As pointed out by BizJournals, Adidas recently filed an appeal with the U.S. Federal Court of Appeals seeking to reverse an Oct. 19 decision that upheld Nike’s patent for the Flyknit technology. The mega brands have been fighting over this issue since 2012, when they each released a knitted footwear design prior to the Summer Olympics. Nike’s Flyknit debuted in February and Adidas Primeknit was released several months later. Unsurprisingly, this sparked an ongoing legal battle.

Shortly after Adidas unveiled the Primeknit, Nike filed a patent infringement claim in Germany. Nike secured a patent in 2004, securing ownership of a knitted shoe upper and the methods of producing it. The court temporarily granted Nike’s injunction, which stopped the sale and manufacturing of Adidas’ Primeknit.

But Adidas won't accept defeat.

The brand has consistently challenged the patentability of Nike’s knitted technology. In its most recent filing, Adidas argued Nike’s method of construction could not be patented because it is not unique. Adidas refers to Title 35, Section 103 of U.S. patent law, which states a patentable invention must not have been obvious “to a person having ordinary skill in the art to which the claimed invention pertains.” Adidas argues Nike adopted a “conventional” process—using a machine to knit a single piece of yarn—that has been utilized by other companies for decades.

Stay tuned to see how this plays out for the sportswear giants.