The case recalls memories of civil service whistleblower Clive Ponting's acquittal on official secrets charges when the weight of the case seemed against him.
In this case, there was never any doubt about what the defendants did. They not only admitted it but publicised it. No wonder British Aerospace was surprised.
But while critics claimed the Ponting jury reached a "perverse" verdict, the women had sought to run the long-standing argument that they had committed a crime in the name of preventing a greater crime.
The idea that some crimes can be committed for the greater good has been accepted by juries down the centuries, keeping it alive in the minds of campaigners with a strong sense of injustice.
Perhaps the fact that three of the four women were unrepresented and addressed the jury themselves played a part. They claimed they had lawful excuse to disarm the aircraft because they were using reasonable force to prevent a crime.
David Pickup, for the prosecution, said the women's "genuine and sincere" beliefs were irrelevant to the issues in the case. But the 12 jurors disagreed, proving that the concept of moral justification is still alive and kicking and that the independence of juries can never be underestimated.
The verdict could even be read as a criticism of Government policy over arms sales.
Joanna Wilson said: "It's a victory for justice, a victory for the people of East Timor and at least the people of Liverpool have recognised a crime has been committed by British Aerospace and the British government."
Angela Zelter said: "The British people know what is right and what is wrong. Now we have to go to the Attorney General and the Court of Appeal to stop this deal now."Reuse content