Peace protestors have lost their Court of Appeal case against Gloucestershire Police's conduct in policing an anti-war demonstration in March 2003.
In the build-up to the US-led war in Iraq, more than 120 people were searched, detained, and returned to London, before they arrived at the military base - home to several American B-52 bombers.
Claiming that the police had acted unlawfully, and breached their human rights, the protestors took the police to court in February this year. The High Court then ruled that the decision to search the coaches and turn the protestors away from the RAF base was not unlawful.
But, it was ruled that the police did not have the right to forcibly escort and return the protestors to London.
Both the police and the protestors appealed against the separate aspects of the original ruling - but the Court of Appeal judges on Wednesday upheld both parts of the original ruling.
Lord Woolf, Lord chief justice and Lord justices Clarke and Rix said the police's decision to "forcibly" return the protesters to London could not be described as "necessary and proportionate".
"The escorting police motorcycle outriders had prevented the coaches from stopping or turning off to use the motorway services, and the passengers were unable to leave the coaches even to relieve themselves. They were virtual prisoners on board their coaches for the duration of the two-and-a-half hour journey back to London."
The assistant chief constable of Gloucestershire Police defended the police's actions, saying: "We have always considered that our responses were proportionate and all our decisions on the day were based on intelligence."
He pointed to the discovery on the coach of body armour, smoke bombs and shields - of which none of the protestors admitted responsibility.
And he added that: "Given these circumstances, and the fact that RAF Fairford, and other military installations in the UK, had been the scene of increasingly destructive disorder in the weeks preceding this incident, the police commander on the ground made the decision to turn back the coaches.
"From day one we have vigorously defended this decision, which was made out of a genuine concern that if the coaches were allowed to proceed it would have resulted in disorder and criminal damage at RAF Fairford."
Fairford Coach Action, the group representing more than 80 people in the case, said a case may be taken to the European Court of Human Rights.
Barry Hugill, spokesman for pressure group Liberty, said the right to protest was "absolutely central to the British way of life" and as such the Fairford anti-war protesters had been denied that right.
A spokesman for Amnesty International said the ruling had "serious implications" for the right to peaceful protest.
"That the courts should back the actions of the police in preventing a peaceful demonstration from taking place sets a dangerous precedent.
"The rights of freedom of assembly and freedom of expression for ordinary British people are hard-won and must not be undermined."