Baseless. Deliberate. Designed to frighten consumers. Nefarious! These are just a few of the barbs MillerCoors has been lobbing at Anheuser-Busch in the wake of Bud Light’s viral “Corn Syrup” advertisement. The ad targets Miller Lite and Coors Light for their use of corn syrup in the brewing process, in one fell swoop attempting to capitalize on the recent distaste for all things corn-syrupy and simultaneously casting MillerCoors as, clearly, behind the times.

It worked. The ad racked up 317 million “impressions” on social media sites and was a clear favorite at the 2019 Super Bowl. If you haven’t seen it, the ad features medieval Bud Light brewers receiving a giant cask of corn syrup, whereupon they exclaim there must be some mistake; “We don’t brew Bud Light with corn syrup!” The brewers proceed to roll the cask of corn syrup to the Miller Lite castle, where the guard at the castle gate replies that they have already received its corn syrup; “Try the Coors Light castle. They also use corn syrup.” Lest the point be missed, the Coors Light castle guard states in no uncertain terms, “to be clear, we brew Coors Light with corn syrup.”

Unsurprisingly, MillerCoors is less than thrilled. On March 21st, Miller filed a lawsuit in federal court in Wisconsin, claiming that Anheuser violated the Lanham Act by engaging in false advertising and trademark dilution by tarnishment. A week later, Miller filed a motion for a preliminary injunction, arguing that the Bud Light ads are causing substantial harm to its brand, which has taken generations to build. Unless the court steps in, Miller’s attorneys argue, the “nearly daily barrage” of Anheuser’s advertisements will cause irreparable harm the reputation of its Miller Lite and Coors Light trademarks.

Trademark dilution is a cause of action which allows the owner of a “famous” mark to seek a judicial remedy against a party whose conduct tarnishes the reputation of its mark. A typical claim for dilution by tarnishment involves a party’s use of a famous mark in a controversial context. A real-world example is a case involving a sex-toy shop called “Victor’s Little Secret.” To prevail on a dilution claim, the owner of a mark must show that its mark is famous and that the offending conduct causes a mere likelihood of harm, rather than evidence of actual harm.

In it’s complaint, Miller argues that it uses corn syrup only as a “fermentation aid,” which is a common practice in the brewing industry. The gist of Miller’s argument is that by highlighting Miller’s use of corn syrup as a fermentation aid, Anheuser-Busch is falsely and knowingly conflating ordinary corn syrup (used by many brewers, including Anheuser-Busch in other beers), with high fructose corn syrup, the derided sweetener commonly used in soft drinks. Miller alleges that Anheuser reportedly conducted focus group testing, which revealed that the average consumer does not understand the difference between them. The advertisement, Miller argues, was therefore designed to create a false impression that Miller uses high fructose corn syrup in Miller Lite and Coors Light.

Anheuser-Busch has yet to file its response, which is due by April 18.

In other news, MillerCoors is gearing up for battle on a second, unrelated legal front. Stone Brewing, the eighth largest craft brewer in the country, has filed suit against MillerCoors, alleging trademark infringement for Miller’s rebranding of its Keystone beers to simply Stone. Although a California District Judge noted that Stone has a “moderately strong” claim against MillerCoors for trademark infringement, the judge declined to grant Stone a preliminary injunction blocking Miller from using the trademark “Stone,” finding Stone Brewing did not establish that consumers are actually confusing the two brands, and thus failed to make a showing it would be irreparably harmed in the absence of preliminary injuctive relief.

MillerCoors’ attorneys maintain that Stone’s claims are meritless.