The co-founder of Palestine Action has won a legal challenge to the home secretary’s decision to ban the group under anti-terrorism laws.

The proscription of Palestine Action, which categorised it alongside the likes of Islamic State, was the first of a direct action protest group and attracted widespread condemnation as well as a civil disobedience campaign defying the ban, during which more than 2,000 people have been arrested.

From 5 July last year, being a member of – or showing support for – the group became an offence punishable by up to 14 years in prison.

Huda Ammori, a co-founder of Palestine Action, challenged the ban at a trial in the high court in London, part of which was held in secret and which concluded in December.

On Friday, three judges, led by the president of the king’s bench division, Dame Victoria Sharp, ruled that the decision to proscribe the group was unlawful.