A High Court decision overturning a conviction for aiding the illegal purchase of paua has called into question convictions obtained using undercover officers since 1996.
It's possible these could number in the hundreds.
Justice Duffy ruled in favour of Thin Thi Vu, whom a district court found guilty of aiding and encouraging another person to buy illegal paua from an undercover fisheries officer.
She was sentenced to home detention and community work.
The grounds of the appeal were that by purchasing the paua from the officer, it was the same as buying it from the Crown, which is allowed under the law.
Justice Duffy says in her ruling that a mistake in drafting the Fisheries Act made the enforcement of the offence provisions ineffective, and that early consideration needs to be given to clarifying the legislation.
Disastrous for enforcement - industry
The Ministry of Fisheries has lodged an appeal against the decision, which the Paua Industry Council says is a disaster for fisheries enforcement.
Council chairman Storm Stanley says the legislation needs to be tidied up.
He says undercover fisheries officers put themselves in danger and if they are to be let down by poorly drafted legislation then someone needs to be kicked.
Mr Stanley says the implications are alarming for an industry that exports up to $50 million worth of paua a year.
Ms Vu's lawyer Paul Heaslip says the law is clear that she did nothing illegal.
Mr Heaslip says the way the law is written, buying paua from, or selling it, to a Crown employee is allowed.
He says the paua in question had already been confiscated by the Crown and was then being used to crack down on the black market.
Mr Heaslip says says he represents some people who may now fit the criteria but there won't be a tidal wave of appeals.
"It's not by any means obvious that just because Ms Vu has been acquitted because of this ruling, that other people are automatically going to be. It's only if they fit the exact same type of circumstances as her and the important point being that the only person she dealt with was a fisheries officer."