The European Patent Office has revoked a patent which threatened to halt sales of HTC and Nokia phones in Germany.
Intellectual property licensor Ipcom had demanded a ban on the two smartphone makers' handsets after they refused to meet its terms.
The dispute centred on rights to a wireless technology developed by Bosch for a car telephone system, which it subsequently sold in 2007.
Ipcom said it would appeal the EPO's ruling.
"The patent will remain in effect until the EPO has made a final decision on this appeal," a spokesman told the BBC.
"As patent '100A' currently remains in effect, today's ruling has no impact on the already-initiated cease and desist orders against HTC."
However, HTC urged Ipcom to reconsider.
"This ruling undermines Ipcom's licence infringement claim against us. We trust Ipcom will now reconsider its opportunistic dispute with HTC and withdraw its legal action against us," said a spokeswoman.
Ipcom first challenged HTC in the German courts in 2009 and won. HTC appealed, but later dropped the case just as it was about to come to court last year.
Ipcom subsequently wrote to retailers and wholesalers demanding they stop selling HTC's 3G devices, threatening to sue if they refused.
Last Friday it also scored a legal victory against Nokia when a German court ruled that the Finnish firm had also infringed Ipcom's intellectual property.
Nokia said it wanted the ruling clarified, adding that it believed it only applied to old handsets, most of which it had stopped selling.
Things continued to go in Ipcom's favour on Tuesday when a judge ordered Deutsche Telekom and Vodafone to halt sales of devices that violated Ipcom's rights.Appeal
The latest ruling now threatens to undo its progress.
Ipcom said that its patent was ruled invalid because one of its features "may be too broad".
However, Rainer Osterwalder, the EPO's deputy spokesman said the office could not confirm the reasons for the action until the written findings had been published.
He added that if Ipcom did appeal it might be "years, rather than months" before the parties involved had a final ruling.
Paul Melin, vice president of intellectual property at Nokia, said: "So far, of 62 Ipcom patents that have come to judgment, none has been found valid as granted. Ipcom needs to recognise its position and end its unrealistic demands."