The Court of Appeal has reserved its decision in a case over whether three activists who attacked a dome at the Waihopai spy base should have to pay damages.
The Crown is seeking more than $1.2 million.
In 2010 a jury acquitted Father Peter Murnane, Adrian Leason and Sam Land on criminal damage charges but the Crown then took civil action against them.
In 2011, the High Court ruled that the activists were liable to pay damages.
However, their lawyers told the Court of Appeal on Wednesday that the spy base was illegally established and didn't act in New Zealand's interests - which meant their clients couldn't be held accountable for the damage they did.
Crown lawyer Austin Power said on Thursday that if property law was interpreted in that way, it could force owners to take matters into their own hands when property was damaged because they couldn't rely on the authorities to act for them.
The activists want a civil jury trial, but Mr Powell said that the complexities of the case might preclude that.