The PSNI and Metropolitan Police acted illegally by spying on Belfast journalists Barry McCaffrey and Trevor Birney to identify their sources.
The landmark ruling was made by the Investigatory Powers Tribunal (IPT) in London in a case brought by the two journalists.
It found that in mounting an undercover surveillance operation, the police’s actions were disproportionate and undermined the domestic and international protections available for the media.
The court has ordered the PSNI to pay £4,000 each to Mr McCaffrey and Mr Birney.
Police had targeted a covert operation at an employee of the Police Ombudsman who was suspected of passing secret documents to the journalists which later appeared in a documentary they made called No Stone Unturned about the 1994 Loughinisland killings.
The film revealed collusion between police and loyalist gunmen who murdered six Catholic men as they watched a World Cup football match in the village.
Mr McCaffrey and Mr Birney were arrested and had their homes and offices raided. They later won a court case which found that warrants used to search their homes had been “inappropriate”.
The High Court found the journalists had acted to protect their sources in a lawful way.
The two men brought their case to the IPT, arguing that there were repeated and unjustified attempts by the police to identify their sources.
In a press conference in London, Mr Birney called for a public inquiry.
“This landmark ruling underscores the crucial importance of protecting press freedom and confidential journalistic sources.
“We hope that the judgment today will protect and embolden other journalists pursuing stories that are in the public interest.
“The judgment serves as a warning that unlawful state surveillance targeting the media cannot and should not be justified by broad and vague police claims.
“The judgment raises serious concerns about police abuse of power and the law, and our case has exposed a lack of effective legal safeguards governing secret police operations.”
Mr Birney added: “Only a public inquiry can properly investigate the full extent of unlawful and systematic police spying operations targeting journalists, lawyers and human rights defenders in the north.”
Film maker Barry McCaffrey told reporters in London: “For this court to have found that a Chief Constable has acted unlawfully, we think is a major embarrassment, and it’s something that needs there to be a public inquiry.
“No other alternative - we need a public inquiry.”
Speaking after today’s judgement, PSNI Chief Constable Jon Boutcher said: “I accept the Investigatory Powers Tribunal’s judgment that due consideration was not given to whether there was an overriding public interest in interfering with journalistic sources before authorising surveillance, which importantly, although it was not directed toward the journalists Mr McCaffrey and Mr Birney, it did impact them in 2018.
“This was one of a number of difficult decisions on a complex and fast moving day for policing in Northern Ireland involving balancing competing interests at pace.
“Separately, the Tribunal found that although officers complied with UK law and procedure at the time, a 2013 authorisation for communications data was a breach of our human rights obligations. I am pleased that the Tribunal found officers acted in good faith.
“Significant changes have already been made since these issues occurred, with the role of the Investigatory Powers Commissioners’ in authorising communications data requests and the Judicial Commissioners in cases involving those who handle confidential information.
“This is a detailed judgment and I will take time to consider and reflect on it and along with the findings of the McCullough Review in due course, to consider what further steps we can take.”
