The arrest in London of a radical French publisher under counter-terrorist powers has been referred to the police watchdog after the reviewer of terrorism legislation found that it was wrong. Ernest Moret, 28, was held for almost 24 hours by counter-terrorist police and asked about his opinion of Emmanuel Macron and participation in anti-Macron protests after he arrived at St Pancras station in April for a book fair. In a damning report published on Friday, Jonathan Hall KC, the reviewer of the terrorism legislation, said the police should not have used schedule 7 of the Terrorism Act to confiscate Moret’s phone and laptop and demand he reveal passcodes to the devices. Hall said this legislation is “powerful” and “must therefore be exercised with due care” and should not be used to stifle the right to protest. In response to Hall’s report, the Metropolitan police referred Moret’s arrest to the Independent Office of Police Conduct. Moret’s lawyer, Richard Parry, said his client was “very pleased” with Hall’s report. “We will now be writing to the Met commissioner asking for a full apology and compensation for all the distress of the detention and everything else that’s followed. “The police shouldn’t be doing this. They really need to get their house in order. Mr Moret has been the sacrificial lamb to highlight the extreme dangers of crossing the line from terrorism into public order policing. It has gone too far.” Hall also called for safeguards to ensure that counter-terror laws are not used to investigate public order issues in future. He said: “The problem with exercising counter-terrorism powers to investigate whether an individual is a peaceful protester or a violent protester is that it is using a sledgehammer to crack a nut.” Hall added: “This was an investigation into public order for which counter-terrorism powers were never intended to be used. The rights of free expression and protest are too important in a democracy to allow individuals to be investigated for potential terrorism merely because they may have been involved in protests that have turned violent.” Hall said schedule 7 powers were “exceptional” and should not be used for public order policing especially now that some leftwing and single-issue campaigners were now the responsibility of counter-terrorist police. Hall said: “Now that left[wing] and single-issue terrorism is part of the core work of counter-terrorism police and MI5, a relatively new area of work where understanding of thresholds may not yet be well developed, there is a risk of recurrence unless modest but additional safeguards are built into the code of practice. I recommend that the code is amended to specify that schedule 7 should not be used for the purpose of public order policing.” Hall also criticised the police for threatening Moret with never being able to travel overseas if he failed to hand over a password to his confiscated iPhone and MacBook. Hall said this threat was “exaggerated and overbearing”. He also said it was wrong of the police to ask about legally privileged conversations Moret had had with his lawyer. Moret’s phone and laptop were returned to him last month after he was informed he would not be prosecuted. Police admitted downloading the sim card to his phone. Hall said he had been assured that the data on the sim had not been disseminated and had now been made inaccessible. Announcing that the case would be referred to the IOPC, Commander Dominic Murphy, who leads the Met’s counter-terrorism command, said the force accepted that use of terrorism powers should be subject to “constant vigilance and attention to safeguards”. He added: “We fully cooperated with this review and we know how important it is that our work is as open and transparent as it can be, so that the public can have confidence and trust in what we do and how we do it.”