Property owners would have to take the law into their own hands if the Court of Appeal accepted the legal argument put forward by three protesters who sabotaged a radar dome at the Waihopai spy base, the Crown's lawyer says.
The Crown is seeking to recover more than $1.2 million in damages from Dominican friar Peter Murnane, teacher Adrian Leason and farmer Sam Land.
The trio cut through alarmed electric fences and slashed one of the two inflatable domes which cover the satellite dishes at the Government Communications Security Bureau (GCSB) spy base at Waihopai, near Blenheim, in April 2008.
A jury acquitted the men of burglary and wilful damage, but the High Court ruled the men were still liable for $1,229,289 in damages.
The trio have appealed that decision in the Court of Appeal, arguing they are not liable for damages because the GCSB's property was being used for illegal espionage which was not in New Zealand's national interests.
The argument relies on a seldom-used legal principle known as `ex turpi causa', which holds that a party cannot bring a claim if they have acted unlawfully.
Crown lawyer Austin Powell said the appellants' argument was a massive extension of that principle which had wider implications for property rights.
Property rights would be "virtually unenforceable'' because police would have to be certain a property was not being used illegally before intervening.
Mr Powell said that would encourage property owners to take matters into their own hands.
"That is not the law. No one has ever said that is the law.''
Mr Powell said owning property in itself could not be illegal, regardless of whether the property was used illegally.
He gave the example of a convicted drink driver who was still legally able to own a car.
"It is not illegal for the Government to own an antenna or buildings or radomes,'' Mr Powell said.
Appeal lawyer Michael Knowles told the court yesterday that the men wanted a civil trial before a jury, to determine whether they owed damages to the spy agency.
He said the GCSB should have to properly prove its case against the men.
Justices Tony Randerson, Lynton Stevens and Douglas White have reserved their decision.
Speaking outside court yesterday, Mr Murnane said the men would not pay damages if the appeal was unsuccessful.
"We have no intention of paying a cent, even if I had it, because I don't believe it's a just case.''