A UK government attempt to remove one of the last remaining defences for climate protesters would be a slippery slope to the erosion of the constitutional right to trial by jury, the court of appeal was told on Wednesday. The attorney general, Victoria Prentis KC, is arguing that one of the last available defences being used by environmental protesters should be removed. Prentis is making the appeal in the case of a defendant known as C, after a string of acquittals by juries of defendants for acts of criminal damage involving daubing paint on buildings. Tom Little KC for the attorney general, told the appeal court judges that use of the so-called “consent” defence under the Criminal Damage Act 1971 was wrong and too broad an interpretation of the law. The defence, which relates to criminal damage only, involves a defendant arguing they had an honest belief that the owner of the property damaged would have consented if they had known the reasons why the action had been taken. Little said climate protesters had resorted to using the defence because another key defence under the Human Rights Act had been removed in a previous intervention by Suella Braverman as the attorney general. “The defence has only recently begun to be run … since the last attorney general closed down one door. Another door has been wrongly broken down in order [for defendants] to make this argument,” he said. But Henry Blaxland KC, for C, said it was a matter for a jury to decide whether a defendant honestly believed that the owner of a property would have consented to the damage caused. “This is a matter for the jury,” said Blaxland. He said to stop a defendant presenting the defence to jurors “would be a slippery slope to the erosion of the constitutional right to trial by jury”. In an exclusive interview with the Guardian, the woman at the centre of the attorney general’s appeal said the attempt to remove the defence was an assault on the rights of juries to acquit defendants. The young woman, who cannot be named for legal reasons, was found not guilty by a jury of criminal damage in a climate trial last year. Speaking to the Guardian, C said: “I was found not guilty by a jury after a long trial. I feel like the attorney general is trying to retrospectively challenge the jury’s decision. It feels like an assault on the rights of juries to acquit someone having listened to the evidence.” Little said he was not seeking some kind of special regime for protesters but rather to seek clarification on the law because trial judges had been making inconsistent decisions on whether defendants charged with criminal damage could use the defence. “We submit that [the defence] is being used in a way that was not envisaged and cannot have been intended by parliament. If that is right, it leads to the conclusion that this section [of the act] is being interpreted too broadly and in reality wrongly.” Several protesters have been acquitted by juries after using the defence in the last year. Among them were climate protesters found not guilty of criminal damage at the London headquarters of HSBC bank and individuals acquitted of conspiracy to commit criminal damage arising from their actions at the party headquarters of the Conservatives, Labour, the Liberal Democrats and the Greens. Individuals protesting for Palestine Action were also found not guilty by juries after using the consent defence last year. As attorney general, Suella Braverman successfully went to the appeal court in 2022 to remove the defence of proportionality for “significant” criminal damage under the Human Rights Act 1998 following her anger over the jury acquittals of four individuals for toppling a statue of slave trader Edward Colston in Bristol. Judgment was reserved until a later date.