If the Golden Age of comic books was 1938-1945 or so, then some might argue that the Golden Age of superheroes is right now. After all, characters like Batman, Spider-Man and the Avengers rake in the dough at the box office and have name recognition with children and adults around the world. Since 1979, the two largest comic book companies in the United States, Marvel Comics and DC Comics, have held a joint trademark over the term “super hero.”

The companies renewed the trademark in 2006, much to the chagrin of many critics who felt that the trademark – which covers a wide variety of products, from comics to playing cards, from costumes to pencil sharpeners and more – was too restrictive.

Independent creators not affiliated with Marvel and DC are forbidden from using the term superhero in their products, as several U.K. residents have recently learned. In March, DC and Marvel filed motion to block U.K. diet supplement company Bio-Synergy from using the slogan “Fuel the super-hero inside,” and in April, they opposed a British author’s attempt to trademark the title of his advice book “Business Zero to Superhero.”  The comic companies have likewise flexed their gamma-powered muscles to protect their trademark in the US as well, including blocking a small press’s attempt to publish a series called “Super Hero Happy Hour,” and another creator who wanted to publish a title called “A World without Superheroes.”

Graham Jules was about to publish his self-help manual “Business Zero to Superhero” in 2014 when he got a letter from Marvel and DC Comics claiming the word infringed their jointly-owned trademark. Jules, a 48-year-old who runs a firm setting up pop-up shops and is studying law, had been about to publish his self-help manual Business Zero to Superhero in 2014, when he got a warning letter from the two companies.

He compiled his entire case without legal aid using a single textbook about intellectual property law – while his giant adversaries armed themselves with the finest legal minds.Mr. Jules estimates he spent a total of just £200 – the cost of registering to fight the claim – plus 200 hours in writing letters.

But after a two-and-a-half-year wrangle with Graham Jules, it is the combined might of the comic book giants Marvel and DC who have raised a white flag after initially claiming that using the word superhero would cause confusion and dilute their brand. Now Mr. Jules can keep the title of his book and finally publish it.