I've notified IGIS of an error relating to the jurisdiction of the recent inquiry, but they haven't referred to the error in their response. Since I'm not expecting any further response from IGIS I have made the emails available to the public on this website.
The crux of their response was that the office of the IGIS was created by the Inspector-General of Intelligence and Security Act. The problem with this is that the right to exercise a public trust that constitutes a legal office is not something that is created by the NZ parliament, since the NZ parliament is not sovereign in the sense of sovereignty in English law. This problem is illustrated in the way that the NZ state misrepresents legal sovereignty (i.e. sovereignty having an ethical basis for exercising a public trust) as political sovereignty (i.e. sovereignty as a function of accountability). Sovereignty was expressed as wisdom, goodness, and power at the time of the inception of the NZ civil state (Blackstone).
A common law interpretation of the language of legislation conflicts with the interpretation of "one law for all" that is used by the state, with the state interpretation more being more like an article of religion than a position based on facts and reason. This is a constitutional issue which has broad implications for democracy in New Zealand.