Patent holding company NTP has filed a lawsuit against Palm, alleging that the maker of the Treo smartphone infringes on the company's patents. 

NTP is a holding company that attempts to collect licence fees for a set of patents covering a wireless email system.

The company is best known for its five-year legal battle with BlackBerry maker Research In Motion. 

RIM settled the case in March with a payment of $612.5m after facing an injunction that would have shut down the service in North America.

NTP also has licence agreements with Nokia, Good and Visto.

The US Patent and Trademark Office is in the process of re-examining two of the NTP patents and issued final rejection notices earlier this year. 

NTP is demanding damages as well as an injunction that bars Palm selling and servicing the products that infringe on its patents.

But the case against Palm could be a much more difficult fight following a ruling by the US Supreme Court in May imposing restrictions on injunctions in patent cases. 

The new rules effectively prevent patent holding companies from using injunctions to bully manufacturers into purchasing a licence for their technology.