Palestine Action will be banned from midnight after a judge refused its request to temporarily block the UK government from proscribing it as a terror group.
On Friday, a High Court judge refused the bid to temporarily stop the ban.
The group then challenged the ruling at the Court of Appeal, which late on Friday evening rejected the last-minute appeal.
It means supporting Palestine Action will become a criminal offence, with membership or expressing support for the direct action group punishable by up to 14 years in prison.
On his decision at the hearing on Friday, denying the group’s request for a temporary block, High Court judge Mr Justice Chamberlain said: “I have concluded that the harm which would ensue if interim relief is refused but the claim later succeeds is insufficient to outweigh the strong public interest in maintaining the order in force.”
The proposed ban, which amends the Terrorism Act 2000, will come into force after being approved by both the House of Commons and House of Lords earlier this week.
The move was taken to ban the group after an estimated £7m of damage was caused to planes at RAF Brize Norton last month, in action claimed by Palestine Action.
Raza Husain KC, barrister for Palestine Action’s Ms Ammori, told the court banning the group would be “ill-considered” and an “authoritarian abuse” of power.
“This is the first time in our history that a direct action civil disobedience group, which does not advocate for violence, has been sought to be proscribed as terrorists,” he said.
In a 26-page judgement, Mr Justice Chamberlain said some of the consequences feared by Ms Ammori and others who gave evidence were “overstated”.
After the ruling, Ms Ammori said “thousands of people across Britain wake up tomorrow to find they had been criminalised overnight for supporting a domestic protest group which sprays red paint on warplanes and disrupts Israel’s largest weapons manufacturer”.
She added: “We will not stop fighting to defend fundamental rights to free speech and protest in our country and to stand up for the rights of the Palestinian people.”
The group then launched a last-minute challenge at the Court of Appeal, which they lost late on Friday evening.
Delivering their ruling, the Lady Chief Justice Baroness Carr, Lord Justice Lewis and Lord Justice Edis said: “The merits of the underlying decision to proscribe a particular group is not a matter for the court.
“This is a matter, under the relevant Act of Parliament, for the Secretary of State, who is accountable to Parliament for the decisions that she makes.”
The court also refused to pause the ban coming into effect pending any Supreme Court bid.
Around 81 organisations are already proscribed under the Terrorism Act 2000, including Hamas, al Qaida and National Action.
The Home Secretary Yvette Cooper announced plans to proscribe Palestine Action on 23 June, saying that the vandalism of the two planes was “disgraceful” and that the group had a “long history of unacceptable criminal damage”.
Mr Justice Chamberlain said an assessment on whether to ban the group had been made as early as March, and “preceded” the incident at RAF Brize Norton.
Four people have been charged in connection to the incident.