Wellington, July 15 NZPA - The Waihopai spy base saboteurs' successful use of the "claim of right" defence was an aberration and no basis to change the law, a legal expert says.

Auckland University law faculty Associate Professor Bill Hodge told Radio New Zealand he was concerned if the Government acted to restrict the use of the defence which was valid in other cases.

Justice Minister Simon Power yesterday said he was going to change or repeal a defence used by three men, Peter Murnane, Sam Land and Adrian Leason, who were acquitted for attacking the spy base near Blenheim. They argued they were driven by a belief that the station caused human suffering and their actions were lawful.

"There is a danger of overreaction in taking away legitimate defences for legitimate people in legitimate situations. This was simply an aberrant case, a rogue case, and I don't think we should base too much law change on one case," Prof Hodge told Radio New Zealand this morning.

Mr Power said yesterday the defence was being used in a way Parliament did not intend when the law was enacted and New Zealand use was out of step with overseas jurisdictions.

The defence can be used in cases such as where a person buys an item not realising the goods were stolen.

"Are you a criminal if you honestly... believe that it is a valid sale? I don't think you should be a criminal in that case," Prof Hodge said.

Intent was important, he said. He did not think there was a wholesale use of the defence in New Zealand.

The Waihopai case was about the jury and nature of charges the men faced rather than how the courts were operating.

"They could have gone down for simple trespass, they could have gone down for simple wilful damage, I think it was the burglary charge that gave the jury that extra opportunity to say, 'well we are sympathetic to these people'."

The protesters were misguided, he said, but had a right to protest but also should pay for damage they caused.

Green Party MP Keith Locke said the defence was valid in the Waihopai case.

"The Waihopai three believed they were also helping people in distress. They offered proof that the Waihopai spy station has been used to spy on nations opposed to the disastrous war in Iraq."

Father Munane said he did not regret his action and would not rule out doing something similar again.

The options Mr Power would look at included requiring defendants to prove they have a claim of right rather than the prosecution needing to prove they do not; requiring a defendant to show that at the time of the offence their actions or beliefs were reasonable; amending some or all of the 14 offences that have claim of right as an element to ensure the defence is not wider than is appropriate; amending the defence so only someone with a legal claim to the property concerned could use the defence; or a total repeal.