Lululemon Athletica claims in its lawsuit filed in the U.S. District Court for the Central District of California that Costco has “unlawfully traded” on its reputation, goodwill and sweat equity by selling unauthorized and unlicensed apparel that uses knockoff, infringing versions of its patents.

Lululemon Athletica has filed a lawsuit against Costco Wholesale, alleging that the warehouse-club chain is selling knockoff versions of its popular activewear through its Kirkland private-label brand.

Lululemon Athletica launched a lawsuit over the weekend against Costco Wholesale, accusing the warehouse retail giant of infringing on its trademarks by selling clothing that is "confusingly similar" to designs trademarked by Lululemon.