Two businesses in Stillwater are in a dispute over the lawn game hammerschlagen, the latest squabble over the rights to hammer nails into stumps for fun.

WRB Inc., which does business as Hammer-Schlagen, this week sued the Lumberjack Company, which operates a bar and restaurant in downtown Stillwater, alleging violations of its trademark and trade dress.

The case follows a similar dispute earlier this year with a Chaska brewery and other cease-and-desist requests nationwide. All highlight the tricky business of trademark enforcement and the provenance of a nail-and-stump activity often associated with Oktoberfest, beer and German heritage.

WRB owns the intellectual property, including the name, logo, slogans and "trade dress" associated with the game. Hammer-Schlagen, or hammerschlagen, involves driving nails into the perimeter of a cross-section of a cottonwood tree stump using a cross-peen hammer.

The game, regularly played while drinking, is sometimes mistakenly thought to have originated in Germany in the 1800s. But hammerschlagen was created by Carl Schoene, who emigrated from Germany to Minnesota with his parents in 1957.

Schoene originally called the game Nagelspiel, after a children's toy in Germany.

He and his parents offered the game at their family restaurant, the Gasthaus Bavarian Hunter near Stillwater, as a way to increase beer sales in the late 1960s.

While there is evidence that Germany has long had a custom of hammering nails into wooden objects as a competitive activity, Schoene and his father-in-law, Mike Wlaschin, developed and codified the set of rules and materials now called hammerschlagen that is commonly used in the Upper Midwest and at German cultural events across the United States.

James Martin, WRB's chief executive, said in the recent lawsuit that the company licensed use of the name, logo and slogans to the Lumberjack in February 2020. After the COVID-19 pandemic resulted in the restaurant's temporary closure, Lumberjack's owner and CEO Sara Jespersen told WRB she would not be renewing her Hammer-Schlagen licensing agreement when it expired in February 2021.

But the Lumberjack continued to offer the game to patrons after the license ended, the suit claims.

Martin said he contacted Jespersen in June to ask if she wanted to renew her Hammer-Schlagen license, which she declined. Jespersen did not respond to a request for comment and has not filed a formal response in court.

It's the latest in a series of legal steps Martin has taken against restaurants, breweries, festival organizers and competitors, something his lawyer Michael Frasier says is necessary to protect the intellectual property.

"He has a lot of licensees nationwide. There are quite a few instances where someone just needs to be told this is a brand, this is a trademark and you can't use it," Frasier said. "They will then either become a licensee or they'll stop."

But sometimes it escalates.

In December, Martin sued Schram Haus Brewery in Chaska over trademark infringement allegations. The two parties settled the matter in March with the judge issuing a permanent injunction that the brewery no longer use the game. Aaron Schram, co-owner of Schram Haus, declined to comment.

In 2018, WRB and organizers for an Oktoberfest event in Spokane, Wash., also settled a trademark dispute.

Other entrepreneurs have tried to create and sell a retail version of the game but were soon slapped with a cease-and-desist letter from WRB.

"We really pumped the brakes on the whole thing," said Marc Johnson, co-founder of MöbileSchlägen, a collapsible, portable version of the stump-and-hammer game, based in New York state. "He's pretty litigious."

Clayton Gray, who co-founded the Stump Company, said his fledgling startup was already facing mounting logistical challenges when Martin sent them a warning note.

"We pretty much closed up shop after that because we didn't want to deal with it," Gray said in an e-mail. "It seems his main job is seeking out copyright infringements over a game he didn't even invent."

Martin's lawyer says trademark owners have to protect their own intellectual property. WRB's website is covered in legal warnings and detailed explanations of what is and is not Hammer-Schlagen.

"My client, in general, is very reasonable about sitting down with people and trying to resolve things without bringing a lawsuit. He doesn't make money off lawsuits. He makes money in operations," said Frasier, Martin's lawyer. "This case was more egregious based on their history."

They allege that the Lumberjack unlawfully used the trademark and trade dress after Jespersen had told WRB she was not offering the game at her restaurant.

Defending the actual trademark is the easy part, said Frasier. That includes the brand name or something that is "confusingly similar to those words," he said, as well as its slogans, such as "Got Wood?" "Get Nailed" and "Whack It."

"Trade dress is more confusing and more nuanced for some people," Frasier said.

He said the best example is the Coca-Cola bottle. While the shape of it serves no functional purpose, consumers associate the bottle's silhouette with Coke.

In the game of Hammer-Schlagen, that trade dress is a stump with nails around the edge of it where a hammer is used to drive nails into it for sport.

"The question is whether someone is using something in a way causing confusion to the consumer," Frasier said. "In this case, we are talking about something virtually indistinguishable, being used in the same geographic region, as competitors. They don't have to be identical."

"If the Lumberjack Company had a 4x4 with nails down a straight line, nobody would be confused," he argues.