This is what Solicitor-General David Collins said in giving his decision, transcribed from Radio NZ:
www.radionz.co.nz/audio/national/news/20071108-1600

I have advised the commissioner that I am unable to authorise the prosecutions that had been sought under the Terrorism Suppression Act. The responsibility for deciding whether to authorise the proposed prosecutions rests with the solicitor-general pursuant to section 9 of the constitution act and the convention that it is the solicitor-general rather than the attorney-general who determines applications of the kind made by the commissioner in a case such as this. This process insures that there is no perception of political influence being brought to bear on what is essentially a legal process. In making my decision I have considered all of the evidence that is available to date, assessed the relevant law, applied the law to the evidence, made an assessment of the likelihood of any prosecutions succeeding and decided whether or not it is ultimately in the public interest for the prosecutions to proceed. My role is therefore different from the police, who are required to investigate suspected crimes and, in a case like this, place that evidence before me to determine if prosecutions should be brought.

The evidence which I have examined has included many hundreds of pages of intercepted communications, a large number of photographs taken by the police during their surveillance operations as well as video footage of events observed by the police. Regrettably not all of the evidence that I have been able to consider will be able to be made public. I know that this is a source of frustration for the police, undoubtably for the media and I'm sure for the general public. However, I can say that in due course a significant body of the evidence will enter the public domain during the course of the hearings of the charges brought under the arms act against the people whose cases I have considered. In considering in detail all of the available evidence, I am very satisfied that the police had a sufficient and proper basis for investigating the activities in question under the provisions of the Terrorism Suppression Act. The police have in my opinion also acted very properly in referring the evidence... (audio feed interrupted)