A Düsseldorf court ruled last December that the Stratocaster’s design deserved copyright protection, praising its “soft curves” and “timeless” look.

Fender has since warned other guitar makers to stop selling similar curved-body guitars in the EU. Yamaha became the fourth company to confirm receiving such a letter this month.

Musikhaus Thomann, the German music retailer which sells Fender products alongside its own Harley Benton range, says the original ruling was full of “procedural errors” and warns Fender’s campaign threatens “diversity, innovation and competition” in the industry.

CEO Hans Thomann noted the Stratocaster itself inspired later innovations, like Eddie Van Halen’s “Frankenstrat,” and argued smaller rivals can’t afford to fight Fender in court, so Thomann is doing it for them.

Fender CEO Bud Cole denied “suing anyone,” calling the letters “thoughtful and respectful,” and said Fender remains open to working with partners while protecting its design as a “steward of the brand”.