eBay has won a first step to changing US patent law yesterday when the Supreme Court agreed to revisit rules under which companies are granted an injunction if they accuse another firm of infringing on patents.

eBay was found guilty of infringing patents owned by MercExchange and ordered to pay $25m in damages. The case centred on eBay's "buy-it-now" feature. But the judge refused to grant an injunction to stop eBay operating and noted that MercExchange existed solely to exploit its patents and makes no attempt to use them commercially itself. Earlier this year that decision was overturned and the appeals court of the Federal Circuit ruled that MercExchange was entitled to an injunction.

To support its case eBay filed a document from law professors specialising in intellectual property who pointed out that a microprocessor may contain as many as 5,000 patents and accidental infringement of any one would allow a company to stop production entirely.

Patents relating to software and business processes have long been controversial and have divided European and US regulators.

The Computer and Communications Industry Association and the Electronic Frontier Foundations are also supporting the case.