A flotilla of kayaks will be launched into Newcastle Harbour on Friday morning to protest coal exports after the protesters won an 11th-hour victory in the NSW Supreme Court overturning a government ban.

Less than an hour before a marine exclusion zone for Newcastle Harbour was due to take effect, Justice Sarah McNaughton ruled on Thursday afternoon that the exclusion zone declared by the state government was invalid and had no further effect.

The protest group, Rising Tide, is calling for an end to new coal and gas approvals, and the imposition of a 78 per cent tax on coal and gas exports to fund the energy transition.

Alexa Stuart, 21, one of the organisers and the plaintiff in the case, said she was “ecstatic” about the court victory, which “gave hope to young people that their voices matter”.

Stuart said about 5000 people were expected at the week-long “People’s Blockade” on the Newcastle Harbour foreshore, with biggest crowds on Saturday.

Last year, the group blockaded the Port of Newcastle for more than 30 hours with kayaks, canoes, paddleboards and other watercraft. Newcastle is the largest coal port in the world and until this year was prohibited from competing with the Port of Botany on non-coal exports.

Last year’s protest had approval from the police for the 30-hour on-water blockade, but more than 100 protesters deliberately stayed longer to be arrested and gain publicity for the cause.

This year the group applied to blockade the harbour for 50 hours but were rejected by police. The group appealed to the NSW Supreme Court two weeks ago but lost.