When You Sign Westpac Banks Terms and Conditions Contract You Agree to

Privacy: Any member of the Westpac Group may obtain, use and disclose information about you where required by law. In addition, you authorise any member of the Westpac Group to disclose your information to the police, government agencies in New Zealand or overseas or other financial institutions where any member of the Westpac Group reasonably believes that the disclosure will assist it to comply with any law, rules or regulations in New Zealand or overseas or will assist in the investigation, detection and/or prevention of fraud, money laundering or other criminal offences.
https://www.westpac.co.nz/assets/Who-we-are/About-Westpac-NZ/General-Ter...

In the case of Nicky Hager the criminals in government and their gang of henchman the NZ Police can use the following against him: Crimes Act 1961

49 Accessing computer system for dishonest purpose

(1) Every one is liable to imprisonment for a term not exceeding 7 years who, directly or indirectly, accesses any computer system and thereby, dishonestly or by deception, and without claim of right,—

(a) obtains any property, privilege, service, pecuniary advantage, benefit, or valuable consideration

READ THIS: http://pundit.co.nz/content/dixon-v-r-an-easy-case-that-raises-hard-ques...

Another piece of legislation that reveals just how much surveillance we are all subjected to by having a bank account is the AML/CFT privacy destroying law: http://www.dia.govt.nz/Services-Anti-Money-Laundering-Index