The High Court has ruled against the police who are trying to avoid paying up if they lose an unprecedented proceeds-of-crime case over a fatal explosion that killed a young welder.
It is the latest twist in a case that has some businesses asking if police are overstepping their powers.
Police are seeking millions of dollars in personal and business assets from Salters Cartage boss Ron Salter, who processes waste oil at Wiri, sentenced for safety breaches in 2017 over the 2015 death of 24-year-old Jamey Lee Bowring.
It is the first time the proceeds-of-crime laws aimed at gangs and drug-dealing have been levelled against a business.
An earlier ruling said police would have to underwrite losses suffered by the Salters if they lost the case.
Police challenged that, but have now lost.
Police Commissioner Andrew Coster had applied to the court for restraining orders over four properties.
The Salters responded by asking police to be held to an undertaking to pay damages if police lost, and High Court Justice Palmer OKed this, saying the business was at risk of financial damage.
Police are still aiming to take this to the Court of Appeal and in the meantime, sought a court ruling to hold off on having to give the undertaking on costs.
Costs could be large; giving an undertaking to expose the taxpayer to multi millions of dollars of losses.
The National Manager of the Asset Recovery Units told the High Court the liability "will be significant and 'cannot at this stage even be estimated, let alone calculated with any precision' ", Justice Palmer's ruling released on Wednesday said.
Commissioner Coster wants the higher Appeal Court to rule on the undertaking "before he considers whether to provide it or to end the proceedings".
The police's lawyer submitted the earlier judgment "contained several serious errors", including whether the undertaking should have been granted and in what form, and argued Salters would not suffer if police held off on complying with the High Court order to give the undertaking.
"He submits the undertaking raises acute issues of public interest and public policy," the latest ruling said.
But Salter's lawyer argued the Commissioner "wants to have his cake, or restraining orders, and to eat it too, by not providing the undertaking", Justice Palmer said.
"He submits there is no public interest in the Commissioner being able to act with impunity."
His latest ruling said the argument in the earlier case was relevant.
Justice Palmer said he "did not find the Commissioner's submissions against an undertaking to be persuasive".
His earlier ruling had said: "The New Zealand Police are made of sterner and more reasonable stuff than to be unduly 'chilled' by an undertaking."