This week's High Court ruling that the raid on Kim Dotcom's Coatesville mansion was illegal represents a substantial body blow to the cause of the commercial and legal interests in the US who want the internet tycoon extradited to face charges of copyright violation.
It is also a huge embarrassment to the New Zealand Police who, acting on the request of a US Federal Prosecutor, staged the spectacular raid on January 20. There was widespread public unease at the time about the "Rambo" style of the raid, which Dotcom described this week as more suited to flushing out a hidden Osama bin Laden than a flamboyant and highly conspicuous tycoon whose home was probably the country's single most famous domestic building. But Justice Helen Winkelmann's ruling finds profound cause for concern on legal grounds.
Police would have been bracing themselves for her ruling since the hearing a month ago at which she openly questioned their entitlement to do all they did on the day.
"They were clearly entitled to search and seize evidence in relation to the [alleged copyright breach] but that did not give them carte blanche to take everything," she said.
Now, consistent with that observation, she has ruled that the search warrants issued by the District Court and used in the raid were invalid because they did not adequately describe the allegations against the internet multi-millionaire and gave police authority to seize too wide a range of items.
But if Dotcom has won this battle, he is a long way from winning the war. His American lawyer, Ira Rothken, has said the ruling was embarrassing for both governments and a "tremendous blow" to the case against Dotcom. That may be unduly sanguine. It remains to be seen what bearing it will have on the August extradition hearing, the outcome of which will be influenced by many factors other than the legality of the original raid.
As the Supreme Court ruling in the Urewera case made plain, evidence obtained improperly, or even illegally, will not necessarily be ruled inadmissible if the charges to which it relates are serious enough. And if the substantive case gets to court in the US, some powerful forces will be arrayed against Dotcom.
Still, this is a salutary rebuke to the police for what seems to have been an unconscionably gung-ho approach.
The idea that when the FBI shouted "Jump!", our police would ask "How high?"was already distasteful enough. The least that might be hoped is that, while jumping, they would show scrupulous respect for our own legal process.