Police searched people entering the camp site near the power station
Two children who were searched at the Kingsnorth Climate Camp have won permission to seek a judicial review of police powers.
The twins, who were then aged 11, had items confiscated during the searches at the camp near Hoo in August 2008.
Officers searched the pair, referred to as E and T, on the grounds they had "reasonable suspicion" they might be carrying prohibited articles.
Senior judges ruled the case involved issues of "general public importance".
Kent Police's attempt to stop the application was rejected on Wednesday.
The children, now aged 12, were taken by their mother to the protest over plans for a new coal-fired power station.
She said her son T was "traumatised and crying" while he waited to be searched "because he thought he would have to go to jail because he had got a sticker in his bag".
Stickers, environmental badges crayons, highlighter pens and a clown's wig were all confiscated by officers, according to their mother.
All three claim the police acted beyond their powers.
Lord Justice Keene said the proceedings raised "issues of some general importance" and ordered a full hearing to go ahead.
He added: "Large demonstrations are a feature of our democracy, and the proper policing of them is itself a matter of some public importance."
Alex Bailin, appearing for the two children and their mother, said the case concerned the legality of a police checkpoint which saw people queue to be searched and issued with "tickets" before being let into the camp.
Richard Perks, appearing for the Chief Constable of Kent, argued the applications should not be treated as test cases.
He said not everyone who attended the climate camp was searched and it could not be said the police operated an unlawful general policy.
Mr Perks also argued that the cases were damages claims by individuals and should be dealt with by the county court
About 1,000 demonstrators attended the camp to protest against plans for a new coal-fired power station at Kingsnorth in August.