Motorsport’s governing body, the FIA, has ruled the Brawn GP car, which has taken Briton Jenson Button to two wins this season, is legal.
A panel heard eight hours of strongly worded evidence on Tuesday after complaints that Brawn, Toyota and Williams, use an illegal diffuser.
And the five International Court of Appeal judges said the designs “comply with the applicable regulations”.
All three teams are free to race in the Chinese Grand Prix in Shanghai.
“The decision comes as no great surprise,” said BBC Radio 5 Live Formula One commentator David Croft.
“Already this season two sets of stewards, an FIA president and an FIA race director have thought that the diffuser design of Brawn, Williams and Toyota was OK.
“It’s a sensible decision for Formula One. The FIA’s court of appeal were highly unlikely, on technical grounds, to go against the decision of the stewards. Seven teams are now playing catch up and have to do something about it very, very quickly.”
Brawn GP team boss Ross Brawn said in a statement following the verdict: “We respect the right of our competitors to query any design or concept used on our cars through the channels available to them.
“The FIA technical department, the stewards at the Australian and Malaysian Grands Prix and now five judges at the International Court of Appeal have confirmed our belief that our cars have always strictly complied with the 2009 technical regulations.”
Brawn GP currently lead the constructors’ world championship with 25 points, with Toyota in second place on 16 points.
A statement from the Japanese team said: “Our team studied the wording of the new 2009 regulations in precise detail to ensure we interpreted them correctly.
“We also made full use of the consultation procedure with the FIA which was a helpful process to ensure our interpretation of the technical regulations was correct.
“Therefore we had every confidence that the design of our car would be confirmed as legal, firstly by race stewards in Australia and Malaysia and subsequently by the Court of Appeal.”