The high court has said a bid to overturn the proscription of Palestine Action as a terrorist organisation can go ahead.

After deliberating for more than a week, Justice Martin Chamberlain sided with the claimant, Palestine Action co-founder Huda Ammori, by deciding her legal challenge should proceed to a full judicial review hearing. This could take place as early as September.

Barrister Raza Husain, acting on behalf of Ammori, described the ban as “an authoritarian and blatant abuse of power” in court last week.

Behind the scenes, home secretary Yvette Cooper is believed to have tried to block the challenge, arguing that it would be inappropriate and unnecessary because the Terrorism Act contains provisions to apply for de-proscription. But this can take years.

The judge is expected to decide this afternoon whether or not to grant a stay on the proscription until the judicial review has reached a verdict, meaning the ban could be suspended immediately.

Today’s ruling against the home secretary adds to mounting pressure over the order, which Justice Chamberlain heard last week has had a chilling effect on the press, politicians and the public.

More than 300 people – including a priest, octogenarians and a magistrate – have been arrested since 5 July, when the ban came into effect, simply for holding signs saying they support the direct action group.

At least one person has been told by police that support for the Palestinian cause in general is now a terror offence, and people have been stopped for holding signs and wearing T-shirts with slogans that are similar to those used in support of the group, but should still technically be legal.

In a witness statement, Novara Media told the high court that the ban has had a stifling effect on our reporting, with a lack of clarity around the law posing a real threat to press freedom in this country.

On Friday, the UN Human Rights Chief Volker Türk described the ban as “an impermissible restriction on rights [to freedom of expression, peaceful assembly and association] that is at odds with the UK’s obligations under international human rights law.”

Following the verdict, Ammori said: “Our fundamental freedoms as citizens of this country are at stake – not just for those of us who have been directly affected and gagged by the ban, but as Justice Chamberlain said today, there has been a wider ‘chilling effect on those wishing to express legitimate political views’ as a result of the ban, making people fearful to speak out against Israel as it commits genocide and starves the Palestinian people to death. 

“We welcome that the high court did not accept the government’s attempt to argue that the home secretary’s decision should not be subject to full legal challenge and scrutiny, especially at a time when protesters – mostly elderly citizens – are being dragged off in police vans, held in detention for over 24 hours, having their homes raided and face criminal prosecution, simply for holding signs [saying] that they oppose genocide and expressing their support for Palestine Action.

“We will not stop defending fundamental rights to free speech and expression in our country and supporting Palestinian people against a genocide being live-streamed before our eyes.”