It looks like Winnie and his mob are trying to hide behind the 6 month deadline for bringing actions under the Electoral Act.
Incidentally, that deadline is still open for their 2007 return - the2007 Return they have helpfully brought to everyone's attention was false.
These Returns are submitted with an appropriately filled out Statutory Declaration. Statutory Declarations are governed by the Oaths and Declarations Act 1957 No88.
Unlawful administration of oaths
(1) No person shall administer, or cause or allow to be administered, or cause or allow to be received, any oath, affidavit, or affirmation relating to any matter or thing in respect of which that person has not jurisdiction or cognisance by some law in force for the time being.
(2) Every person who wilfully acts in contravention of subsection (1) of this section commits an offence, and is liable on summary conviction to a fine not exceeding $100.
In Australia to lie on a Stat Dec is treated as perjury - I am not sure if that is the case in New Zealand. It is certainly an offence as outlined in the Act.