> The shape of the guitar is very old (75+ years)

They are basing their claims on copyright[1], which is longer than 75+ years[2]. The first case they filed (in Germany, against a Chinese manufacturer) "validated" their copyright claims because the Chinese manufacturer did not turn up to court so the court ruled in Fender's favor in a default judgment. The small companies being sued could still fight Fender in court and overturn that default judgment, but court cases are expensive and Fender is massive. It's Fender abusing the courts to bully their competition.

[1] "The Dusseldorf court deemed that the Stratocaster design qualified as a copyrighted work of applied art under German and European law, thus prohibiting Yiwu Philharmonic Musical Instruments Co. from manufacturing, offering or distributing guitars featuring the Stratocaster body shape in Germany and the EU." https://www.guitarworld.com/music-industry/fender-legal-ruli...

[2] "The chosen term for a work was 70 years from the death of the author." https://en.wikipedia.org/wiki/Copyright_law_of_the_European_... Leo Fender passed in 1991, so any copyrights attributable to him expire in the year 2061 (ie another 35 years from now, more than 100 years after the first strats were sold). I'm not 100% sure this is the copyright situation Fender asserted, but it's probably something not very far off from this. If you think this copyright duration is absolutely ludicrous, you are correct.

Patents and trademarks would not cover it, but fortunately this case was about copyright.

Trademarks are infinite though. Which makes sense, since otherwise anyone could produce "Coca Cola".