The co-founder of Palestine Action has said the battle to overturn the terrorism ban on the direct action group will be won – in the courts or “on the streets”.

On Monday, five court of appeal judges ruled that a ban on the organisation was lawful, reversing the high court’s February judgment, which they said had wrongly limited the home secretary’s discretion on national security.

Huda Ammori, who as a founder of Palestine Action – the first direct action protest group to be banned under the Terrorism Act – brought the legal challenge, said she was disappointed but remained confident of victory.

“I‘m certain that legally we are correct that this ban is disproportionate to free speech and the right to protest. I think that’s really clear,” she said. “We just need to get to the right court that’s going to recognise that and we’ll take it all the way up to the European court of human rights, if needs be.”

At the same time as the legal challenge has gone through the courts there has been a civil disobedience campaign with more than 3,000 people arrested, mainly for holding placards supporting Palestine Action. Another 117 were arrested outside the court of appeal on Monday as well as two outside the Old Bailey, where a criminal trial involving activists from the group is taking place.

Ammori said such defiance remained key. “This case is completely political, and the way we are going to win this is on the streets,” she said. “Everyone who sacrificed and stood up against this, all of that is bringing us closer and closer to the day when we are victorious.”

As an illustration of what she termed the politicisation of the case, Ammori highlighted the court of appeal judges’ assertion that “Palestine Action has little or nothing in common with the suffragettes”.

The suffragettes carried out a nationwide bombing campaign while Emily Davison, who is commemorated by two statues, attacked a clergyman with a horse whip after mistaking him for the then chancellor, David Lloyd George. Ammori said of the judges’ comparison: “It just is completely inaccurate and quite crazy that they even felt like they needed to make that comparison.”

Monday’s judgment was the second blow for Palestine Action after Friday’s sentencing of four activists involved in a 2024 raid on an Israeli manufacturer’s arms factory near Bristol.

They were convicted by a jury of criminal damage for smashing up drones and other equipment at the Elbit Systems UK site – having been restricted by the judge in what they could say about their motivations for their acts – and in one case of grievous bodily harm without intent. At the sentencing the judge ruled there was a “terrorist connection” – which had never been put before the jury – to the criminal damage charge.

“It feels like that this whole thing has been orchestrated to ensure convictions and show people can be sentenced as terrorists to then justify the ban on Palestine Action,” said Ammori.

Despite the setbacks, she urged supporters to stay strong. “Remember, who we are acting in solidarity with, which is the Palestinian people, who, despite all of the setbacks and challenges they face, including being labelled as terrorists, are continuing to resist for their freedom,” she said. “And [remember] that we are acting in solidarity with them and we can take strength from the Palestinian people and that whenever there is repression, there is more resistance.

“The way that we respond to this is by fighting even harder, that every struggle has its setbacks. But we are going to win in the end. We can’t give in. We can’t be deterred.”

The home secretary, Shabana Mahmood, said: “The court has found that Palestine Action has carried out acts of terrorism, celebrated those who have taken part in those acts and promoted the use of violence. It is not an ordinary protest or civil disobedience group, and its actions are not consistent with democratic values and the rule of law.

“This decision does not affect lawful protest in support of the Palestinian cause, which remains a fundamental democratic right. There is a difference between supporting Palestine and supporting a proscribed terrorist group.

“We will always take the strongest possible action to protect our national security and keep the public safe.”