Protesters arrested for allegedly supporting Palestine Action have expressed anger at the court of appeal’s decision that the ban on the direct action group was lawful.

On Monday, five judges overturned the high court’s February ruling that proscription was unlawful, meaning that more than 3,000 people who have been arrested under the Terrorism Act since proscription, more than 700 of whom have been charged, could now face prosecution.

While the Palestine Action co-founder, Huda Ammori, has said she will appeal to the supreme court, any prospect of the ban being quashed and prosecutions being discontinued – which seemed a possibility after the high court judgment – is off the table for now.

One of those charged, Deborah Hinton, 82, a former magistrate from Truro, Cornwall, described the judgment as “devastating and shocking”. She said of a prison sentence under the Terrorism Act: “Obviously I’m very upset, I’m very nervous, but I couldn’t do anything else but do what I did. I didn’t have a choice. We are heading towards an authoritarian state, and as I saw it, it was my duty to take a stand.

“One did hold out hope that the government [would] see sense. We haven’t got enough money to have a proper defence system for this country and yet they’re wasting millions and millions on this ridiculous prosecution of people holding placards.”

The vast majority of those arrested were holding placards saying “I oppose genocide, I support Palestine Action” at Defend Our Juries demonstrations.

Marianne Sorrell, 81, from Wells, Somerset, who was held by police for almost 27 hours after being arrested, during which officers forced their way into her house and searched it, described Monday’s judgment as a travesty of justice. “I’m thinking very seriously of getting arrested again for the same offence,” she said.

“I haven’t up to now, because it meant going to London but I’m so incensed by what’s going on and very perturbed that I’m thinking I will go to London if the action to support Palestine Action is to continue.”

Both Hinton and Sorrell also expressed outrage about the lengthy custodial sentences imposed on Friday on four Palestine Action activists who smashed up drones and other equipment at an Israeli arms manufacturer’s UK factory after a judge ruled that there was a “terrorist connection” to their offending. Hinton described it as “completely out of all proportion and of anything that one could expect in a civilised country like ours”.

Father John McGowan, 75 – who was one of 532 people arrested at a demonstration in Parliament Square on 9 August last year, said he too was angry and disappointed by the court of appeal’s decision but it did not affect how he felt about what he did.

“[Being arrested and charged] is an inconvenience for me compared to what the people are currently experiencing in Gaza, and still are,” he said. “My judge is myself, my conscience, I’m at peace with myself and with what I’ve done and so let’s see what happens. I’m prepared even to go to prison. I don’t think that will happen but I’m prepared to do that.”

In her written judgment on Monday, the lady chief justice, Sue Carr, said: “When the severity of the effects of proscription on [an individual’s rights to freedom of expression and assembly] are balanced against the importance of the objectives of protecting national security and the rights and freedoms of others … we find that the latter in this case outweighed the former.”

The court of appeal’s decision also prompted renewed criticism of the ban from human rights groups.

Tom Southerden, Amnesty’s legal programme director, said: “We have long said that the banning of Palestine Action as a terrorist organisation was a grave misuse of sweeping counter-terrorism powers with serious consequences for human rights, and today’s outcome does not alter that assessment. It is fundamentally disproportionate to treat direct action protest as terrorism.

“The images of people from all walks of life – from nurses and pensioners to military veterans – being bundled into police vans for peacefully holding placards will be long remembered as a deeply shameful chapter in our history.”