A 94-year-old peaceful protester has won an eight-year legal battle to force the police to delete details of his political activities from a secretive database.

On Thursday, the European court of human rights ruled in favour of John Catt, noting he “had never been convicted of any offence and his risk of violent criminality was remote”.

The activist had argued police were not justified in retaining 66 records of his activities at peace and human rights protests. They contained descriptions of his appearance and clothes at the protests and how he liked to draw sketches of the demonstrations.

The eight European judges decided police had violated his human rights as they had no pressing need to retain the records on a database of “domestic extremists”. They added that the database did not have effective safeguards to protect the rights of protesters.

Catt’s lawyer, Shamik Dutta, said he had been vindicated. “This ruling sets an important precedent that it is unlawful for governments across Europe to label citizens engaged in peaceful protest domestic extremists and put them on a searchable database for a potentially indefinite period,” he added.

Campaigners called on police to close down the secretive databases they hold on protesters. Forces have been criticised for retaining secret files on the political activities of thousands of campaigners, including the Green party politicians Caroline Lucas and Jenny Jones.

The files on Catt had been collected and stored by a secretive police unit whose undercover operations infiltrating political groups caused controversy.

Catt, who lives in Brighton, has been a peace campaigner since 1948. In 2010, he used the Data Protection Act 1998 to discover police had conducted surveillance on him at demonstrations between 2005 and 2009.

Most of the records concerned a campaign to close down an arms factory in Brighton, while others logged his attendance at a trade union conference in 2006 and a demonstration at the Labour party conference in 2007.

They recorded how he “sat on a folding chair … and appeared to be sketching” at one demonstration. Another noted at a different protest, “he was using his drawing pad to sketch a picture of the protest and police presence”.

The records had been kept by the now defunct National Public Order Intelligence Unit, which police said was tasked with monitoring protesters who used criminal methods to promote their cause.

In their verdict, the judges said police were justified in collecting the information as the group campaigning against the Brighton arms factory were known to be violent and potentially criminal.

They added that while Catt had never been violent, he had identified himself repeatedly with the group, which is known as Smash EDO.

However, the judges said police were not justified in retaining the records on Catt, as they contained personal data including his political opinions, which should have a heightened level of protection from state surveillance.

They said it was accepted Catt did not pose a threat to anyone and noted police did not have effective safeguards on the database, particularly as there were no rules on how long files on individuals should be kept for.

The judges said they were concerned police had no clear definition of what constituted “domestic extremism” and, in Catt’s case, did not appear to have respected their fluid definition to recognise he was a peaceful protester.

Kevin Blowe of the Network for Police Monitoring civil liberties group said: “This case highlights concerns Netpol has raised repeatedly over the past decade about the extremely flexible misuse of the ‘extremist’ label against political activists and the unlawful retention of information about them by the police.”