The wacky case of Costco’s coveted golf balls continues with a new wrinkle: Costco is suing Acushnet Company, a premium ball maker, over comments made about the Kirkland Signature ball.Costco’s ball became a sensation last year when its price point ($15 per dozen) and high performance caused them to sell out repeatedly. Rumors flew in January that Costco’s manufacturer, Korean company Nassau, had finally sold out of the ball. But Costco assured customers that the Kirkland Signature ball would be back next month, according to Golf Digest.

But the balls’ cult popularity has rubbed some the wrong way, like Acushnet, the makers of Titleist golf balls. They sent Costco a letter alleging false advertising because of its Kirkland Signature guarantee, which says all products will “meet or exceed the quality standards of leading national brands”). Acushnet also said Costco’s balls infringe on the company’s 11 patents.

Costco is ready to swing back. The Kirkland-based corporation hit Acushnet with a declaratory judgement to establish that not only is Costco not guilty of false advertising or violating Acushnet’s patents, but that the patents are invalid to begin with.

The suit, filed in U.S. District Court’s western District of Washington at Seattle, notes reviewers and golf pros have compared more expensive “tour quality balls” sold by brands such Titleist, Callaway and TaylorMade, to Costco’s, the company “has never publicly compared the KS ball with any Acushnet ball.”

Costco may be in for a bit of a legal ride. Though declaratory judgments like this are usually a preemptive strike (a lawsuit to stop a lawsuit), Acushnet has been game to play through in the past.

The Korean company holds more U.S. patents in golf ball technology (at least 1,200) than any other manufacturer, and they have a history of stepping up to the tee to defend their patent portfolio, even through years of litigation. Invalidating patents is never easy, but going against a company with the intellectual property and the guns to back it up makes it that much harder.

Either way, Costco seems ready to tee off with this lawsuit. Now it’s Acushnet’s turn to file an answer to the suit.