A man from Brighton who wants records of his political activities removed from a police database has taken his case to the Court of Appeal.
John Catt, 88, who has spent years protesting about issues but has not engaged in any criminality, said the retention of data on a police database was unlawful.
High Court judges last year ruled his human rights were not being infringed.
He is now asking the Appeal Court to overturn that decision.
Mr Catt began legal action after he discovered details of his protests against Brighton-based arms factory EDO were being held on the National Domestic Extremism Database.
'Contravenes human rights'
Mr Catt's lawyer, Shamik Dutta, said: "If the appeal is successful, police forces will need to review the way in which they gather and retain information about protesters who have never committed any offence."
The Equality and Human Rights Commission said the retention of personal information on the database contravenes peaceful protesters' human rights.
The commission's John Wadham said: "The right to protest peacefully in public is a core human right and any measures that restrict this right should be subject to proper scrutiny.
"The police now need to take measures to ensure that the information they hold does not contravene the law."
Lord Justice Gross and Mr Justice Irwin dismissed Mr Catt's claim at a hearing in May 2012, ruling that his right to privacy under the European Convention on Human Rights had not been infringed.
Mr Catt is now asking Master of the Rolls Lord Dyson, Lord Justice Moore-Bick and Lord Justice McCombe, to overturn that decision.
The hearing continues.