The GCSB has a credibility problem

Last month, NSA whistleblower Edward Snowden gave evidence to the European Parliament, in which he revealed that the NSA were "advising" their "partners" on how to interpret mass-surveillance-enabling "loopholes" into their spy-laws. New Zealand was specifically mentioned as having received such advice:

In recent public memory, we have seen these FAD "legal guidance" operations occur in both Sweden and the Netherlands, and also faraway New Zealand.

This naturally raised the question of exactly what GCSB had received "guidance" on, and whether the NSA had written John Key's spy bill (which contains some very careful loopholes which enable mass-spying). So I did what I always do, and sent in an OIA request asking whether they had received advice from any foreign agency on the interpretation of their governing Act. Last week, I received the response [DocumentCloud]: a categorical denial:

The GCSB has not received any guidance or advice on how to interpret the GCSB Act or on any amendments to the GCSB Act from any foreign agency or government. As such I decline to provide the information requested under the provisions of section 18(e) of the Official Information Act (the Act), on the grounds that the information requested does not exist.

That's pretty clear, and there doesn't seem to be any wiggle-room to turn it into a non-denial "denial". At the same time, the GCSB has a credibility problem here, because its answer clearly contradicts Snowden's evidence. So, who do we believe? A secretive government agency with every reason to lie, or a whistleblower with none? That's a no-brainer - and if Snowden produces a single document backing up his claim, then Ian Fletcher's head should be on a spike.