The GCSB's excuse for its unlawful spying on New Zealanders was that the law was "unclear". When it said
Neither the Director, nor an employee of the Bureau, nor a person acting on behalf of the Bureau may authorise or take any action for the purpose of intercepting the communications of a person... who is a New Zealand citizen or a permanent resident.
it apparently, against all logic, didn't mean it.
So was it the intent of Parliament to give them an excuse, to enact an apparently absolute prohibition but add a "not really" somewhere? I've just spent some time reading the Parliamentary debates on the passage of the GCSB Act, and the answer is a resounding "no". For example, here's Michael Cullen introducing the bill at its first reading:
Clause 16 permits interception of foreign communications without a warrant in specified circumstances. That simply preserves the bureau's existing abilities to intercept such communications under existing law---subject, of course, to clause 14. That means the bureau is not permitted to take any action for the purpose of intercepting the communications of a New Zealand citizen or permanent resident unless that person is acting as a representative of a foreign organisation.
Clause 17 sets out the conditions on the Minister issuing an interception warrant. The emphasis is explicitly on foreign communications... Clause 20 sets out the conditions on the issue of a computer access authorisation, which may relate only to computer systems of foreign persons or foreign organisations
In particular, this legislation makes it clear that the bureau's signal intelligence operations do not target the communications of New Zealand citizens. That is not simply a matter of faith, it is confirmed annually in the reports of the Inspector-General of Intelligence and Security.
The interception powers relate specifically to foreign communications... So the legislation, particularly clause 14, makes it absolutely clear that communications by New Zealanders are not the target of the bureau.
And Simon Power, at the committee stage:
[C]lause 17, which relates to the issuing of the interception warrant, is completely subject to the restrictions imposed by clause 14. In legal terms, the bar is actually set quite high for those who are seeking to obtain or intercept information by one means or another.
The will of Parliament was pretty clear: the GCSB wasn't to spy on New Zealanders. The GCSB violated that. And they need to be held to account for it, not excused and given broader powers.