Charges have been dropped against the majority of a group of Wellington peace activists arrested after protesting at a Defence Industry Association gathering in 2015.

Photo: RNZ / Kate Gudsell

Fifteen people went on trial in the Wellington District Court on Monday, but only six are still before the Court.

Those whose charges were dropped included one of the so-called "Waihopai 3", Adrian Leason and veteran Wellington peace activist, Valerie Morse.

The police case against several of the protesters collapsed after a key witness, the owner of the weapons conference venue TSB Arena, admitted there was an easement around it, meaning the protest was not on private land.

On Tuesday the police lawyer, Catherine Gisler told Judge Ian Mill no further evidence would be offered in respect of nine of the defendants.

The defendants' supporters had packed the public gallery and applauded as the judge discharged each of them.

After being discharged, Ms Morse told the Court she intended seeking costs from police, claiming they had used the court as a vehicle to punish the activists.

"If they'd spent half as much time as they did seeking to shut down lawful protests determining they didn't have the appropriate power to do that, we wouldn't be here wasting the crown's time the court's time and any of our time."

Ms Morse said some defendants had taken the option of pleading guilty and sought police diversion soon after the charges were laid because their circumstances did not allow them to continue with the court action.

She said those involved in the case had paid an enormous price financially and emotionally in preparing for the trial.

"The police have abused this process as a means of oppressing legitimate dissent and I am seeking the court's leave to apply for costs and hope you will look upon that favourably."

Judge Mill asked Ms Morse to put her application in writing and said he would consider it later.

The police case against the remaining six defendants then continued, with evidence from Alex Hampshire, a manager for Wilson Parking, which ran the TSB Arena carpark.

He said a representative of the venue contacted him before the conference and asked him to provide a signed trespass notice in case there were any problems.

Mr Hampshire said he did so and the trespass notice wording said it was to "warn any person whose behaviour is inappropriate in terms of the conditions of entry to the establishment".

In response to questions from defence lawyer Daniel Vincent, he said that would be behaviour that was inappropriate in a public space.

When asked to explain how that would be judged, the witness said it would be according to "generalisations" which he said he had not communicated to the police.

Mr Hampshire admitted that conditions of use for the carpark related to people entering it in vehicles, with no conditions posted for people going in without a car.

The case is continuing.