The high level of media interest in the Harry Potter copyright case heard in New York last month was perhaps inevitable given the popularity of anything to do with the young wizard.

However, the case raises an issue that will be of particular interest to both authors and trade mark owners whose works or products attract internet fan sites, and to those operating or posting material on fan sites. At what point should a copyright or trade mark owner take steps to enforce their rights against fan sites that are promoting their works or products?

In bringing a copyright infringement action against the publisher of The Harry Potter Lexicon — a readers’ guide to characters, places and spells in the Harry Potter books — J.K. Rowling turned on one of her greatest supporters.

Where to draw the line between legitimate fan club activities and activities that impinge on copyright or trade mark rights is something that has exercised many intellectual property owners in recent years. On one hand, it is important not to alienate one’s most loyal supporters. On the other, it is important that appropriate control is retained over use of the protected work.

This is the issue that confronted Rowling. It seems that she chose to draw the line between the non-commercial activities that had been undertaken on the internet by the fan club, which were acceptable, and the clearly commercial hard-copy publication of the lexicon, which was not.

The author of The Harry Potter Lexicon was what has been described as a Harry Potter “superfan” who ran a popular fan site on which he originally published the lexicon free of charge. Rowling both knew of and approved of the site, apparently even giving it an award; she sometimes used the online lexicon as a reference tool.

But she had two grievances. First, much of the lexicon’s text had been taken directly from the Harry Potter books and then put into a simple A to Z format. The defendant, she claimed, had made very little real contribution. She was particularly galled by the fact that so much of her text had been used without any quotation marks. If quotation marks had been used, she said, it would have been necessary to use them on virtually all the lexicon text. Second, she herself intended to produce a lexicon of the Harry Potter books and to pay the proceeds to charity. Publication of the defendant’s lexicon would seriously undermine that exercise.

The central issue in the case is the extent to which use can be made of a copyright work in the preparation of reference guides without infringing copyright, and the circumstances in which a defendant can rely on the defence of “fair use”.

If, as Rowling and Warner claim, much of the defendant’s work has been lifted directly from the Harry Potter books, it is likely that the defendant will be found to have infringed copyright. The issue for the court then to consider will be whether publication of the lexicon amounts to “fair use”. If it does, there will be no infringement.

The defence of “fair use” is available in the US for reproductions of copyright works for purposes such as (but not limited to) criticism, comment, news reporting, scholarship and research. In determining whether a particular use is fair, the factors to be considered by the Court must include: the purpose and character of the use, including whether such use is of a commercial nature or is for non-profit educational purposes; the nature of the copyrighted work; the amount and substantiality of the portion used in relation to the copyrighted work as a whole; and the effect of the use upon the potential market for or value of the copyrighted work.

What weight a particular court may give to each of these factors, and what other factors it might consider relevant, is always notoriously difficult to predict. In this case it is almost impossible.

In considering the first factor, the court will no doubt place much emphasis on the extent to which the defendant’s work goes beyond the original work, either advancing knowledge or progressing the arts. On the face of it, the lexicon provides a tool that will aid in the understanding and interpretation of the Harry Potter books, which are acknowledged to be complex. It is a tool that has apparently been in great demand.

On this basis, the court may well consider that it goes considerably beyond the original work and it may choose to place less weight on the clearly commercial nature of the lexicon. On the other hand, the court may be influenced in favour of Rowling by the fact that the lexicon has relied so heavily on, and is so closely tied to, the original work.

Another factor that may influence the court in Rowling’s favour is that although publication of the lexicon is not likely to have any negative effect on the value of, or market for, the Harry Potter books, it may very well have a negative effect on the potential market for Rowling’s own proposed lexicon. On the other hand, the court might consider that the her failure to take any action in relation to publication of the lexicon on the internet has encouraged the defendant to proceed, and that he should be entitled to do so.

Whatever the outcome, the court’s decision is likely to provide welcome guidance for copyright and trade mark owners on the implications of permitting their intellectual property rights to be used freely on the internet. If you want to control future use of your copyright works and trade marks, you may need to take action against unauthorised use that at the time seems unobjectionable.

The question will always be where and when to draw the line. And in the case of activities on fan sites, it might be a good idea to agree limits at the outset, thereby minimising the risk of alienating some of your most valuable customers.

Karen Fong is managing partner and James Elliott a trainee solicitor at Rouse Legal

Explore Law

• Columnists

• Law Panel

• Law Reports

• Student Law

Times Recommends

• The best legal yarns this Christmas
• Legal school 'earned £1m by exploiting bar course'
• Axe may fall on 5,000 more City lawyers