Cayo Evans was the leader of the Free Wales Army
Police have denied they tried to use CCTV to monitor people at the funeral of a Free Wales Army (FWA) supporter.
Machynlleth Town Council has written to the force to complain and the man's widow is asking for an apology.
Up to 60 people walked through the Powys town as a "mark of respect" after Glyn Rowlands's funeral service.
But Dyfed-Powys Police said they wanted to use CCTV to ensure that the "free flow of traffic in Machynlleth could be maintained".
Glyn Rowlands died on 22 August, aged 71, and his funeral was on 1 October.
He had been a member of the FWA, which achieved notoriety when in 1969 two of its members were jailed for 15 months for public order offences.
Under pressure to do something about the protests against Prince Charles' investiture as Prince of Wales, the police arrested nine FWA members in dawn raids.
A 53-day trial finished on the day of the investiture and effectively ended the organisation's brief spell in the national spotlight.
Mr Rowlands was one of nine men prosecuted in 1969.
Machynlleth mayor Sylvia Rowlands, whose husband was Glyn Rowlands's cousin, said the police were "a little bit out of order".
"The town clerk Mr [John] Parsons has written to the police on our behalf," she added.
"We feel it was a little bit out of order. Police wanted to use CCTV to monitor the march, but they didn't in the end.
"There was quite a strong police representation, but it was a funeral for a man respected in the town."
Mr Rowlands's widow Glenys said police had "overreacted".
"What right did they [police] have to be there? He was one of nine people prosecuted [in 1969], but he was found not guilty," she said.
"The walk through Machynlleth was a mark of respect and was not a rally."
Mrs Rowlands claimed plain-clothed police officers were at her husband's funeral at a chapel in nearby Corris in Gwynedd, and were later seen in Machynlleth where there was a procession through the town in memory of Mr Rowlands.
"I've asked the police for an apology and would like to meet the officer in charge that day," she added.
"There was never going to be any trouble."
Dyfed-Powys Police said they had wanted to use CCTV to monitor the flow of traffic.
Supt Meredith said: "I can confirm that on the day of Mr Rowlands's funeral a request was made to Machynlleth Town Council to view the CCTV system.
"However, the purpose of this was solely to assess the number of persons attending the funeral in order that the free flow of traffic in Machynlleth could be maintained.
"At no point was any surveillance undertaken of any individual attending the funeral."