The government’s most senior law officer is to appeal against a decision not to allow a contempt of court action against climate campaigner Trudi Warner for holding a placard on the rights of jurors outside a British court, the Guardian can reveal. Mr Justice Saini ruled at the high court last month there was no basis to take action against Warner, 69, for holding up the sign informing jurors of their right to acquit a defendant based on their conscience. He said the government’s claim that her behaviour fell into the category of criminal contempt was “fanciful”. Saini in his ruling accused the government’s solicitor general of “significantly mischaracterising” the evidence, when his lawyers alleged Warner behaved in an intimidating manner, confronting potential jurors outside the court. His ruling also reiterated that there was a well established principle in law of jury equity; a de facto power to acquit a defendant regardless of directions from the judge. But lawyers for the solicitor general, Robert Courts, have informed Warner’s lawyers they are appealing against the decision. It is another chapter in a year-long legal action against Warner for her lone protest outside the court at the start of a trial of Insulate Britain protesters for a peaceful roadblock. Warner’s sign was in reference to a 1670 landmark case which cemented the independence of juries, known as “Bushel’s case”, in which a jury refused to find defendants guilty despite having repeatedly been instructed to do so by the judge. Warner’s placard read: “Jurors, you have an absolute right to acquit a defendant according to your conscience.” She acted after judge Silas Reid forbade protesters from mentioning climate breakdown as part of their defences. On learning of the further legal action by the government to pursue her for contempt of court – which could carry a two year prison term or a fine – Warner said: “It feels really shocking, to be honest. They clearly want to make an example of me. In a sense I am not surprised, but this is just more public money, and it is shocking.” Warner stood outside inner London crown court last March for 30 minutes holding the placard as members of the public, lawyers and potential jurors filed into court. She held the sign on the first day of a trial for public nuisance of members of the climate campaign group Insulate Britain. The following day she was handcuffed outside the court, and put into the dock before the judge. He referred her action to the attorney general who sought permission at the high court last month to pursue her for contempt of court. A spokesperson for the solicitor general has been contacted for comment.