The 'claim of right' defence is set to be changed after three men accused of wilfully damaging the Government Communications Security Bureau's Waihopai spy base were acquitted using the defence.
The Ministry of Justice says courts have extended the scope of the defence beyond what Parliament anticipated when it made the law in 1961, and the law's out of step with countries like England, Canada, and several Australian states.
Justice Minister Simon Power says Cabinet has agreed to amend the defence so it only applies to people with an interest in the property concerned.
That ensures defendants who make an honest mistake in believing they had a right to deal with the property in the way they did, won't necessarily be held criminally responsible for their actions.
The value of the damage caused by the Ploughshares group is estimated to have been more than $1 million.
3 News / RadioLIVE