When it comes to fictional brands such as the new Duff beer, the trademark laws are far from clear, says Jeremy Dickerson

A German company is brewing and selling Duff Beer, a brand best known as Homer Simpson's tipple of choice.

While fictional brands such as Wonka Bars and Bertie Botts' Every Flavour Beans have previously been brought to life, Duff is unusual in that it does not have the support of Twentieth Century Fox, the producer of The Simpsons.

The German version of Duff is not the first in the 1990s an Australian company sold several thousand cans of Duff before legal action by Fox prevented further sales. Fox is also undertaking legal action in Mexico, and has recently filed trademark oppositions against third-party applications for Duff, which would cover beer.

So while the Duff beer brand is probably as well known as Carlsberg, what intellectual property rights does Fox have to the Duff name given that it is purely fictional and they do not themselves sell beer? What would prevent you from manufacturing another well-known fictional brand South Park's Chocolate Salty Balls perhaps?

Creators of a fictional brand may have a trademark covering the relevant product, permitting them to sue for trademark infringement, particularly where merchandising is anticipated. However, a trademark for a particular product may be challenged and removed from the trademark register after five years if it hasn't been used for a real-life product. A trademark simply for 'merchandising services' may not suffer the same consequences.

The other hurdle comes from the popularity of merchandising itself. Although a product's fame may be due to fictional use only, consumers expect to purchase merchandise for popular shows.

The law of 'passing off' may protect the fictional brand where consumers would expect a real-life product to be endorsed or licensed by the creators of its fictional counterpart. The creator must also prove that they would suffer damage as a result perhaps due to a lost opportunity to take advantage of the brand themselves.

The law in this area is far from settled and, as ever, is complicated. Watch this space.

Jeremy Dickerson is a partner at the law firm Burges Salmon