NZF defines an NZ player as "a player who holds New Zealand citizenship."
You need 8 in your squad, except in the final where you need 9 (but have 2 extra subs).
Some more up-frontness from NZF around who exactly has NZ citizenship would be cool.
For Canterbury, I think it goes like this - though Tom Schwarz must be bloody close (assuming he wants NZ Citizenship, his choice).
Felix Komolong (Papua New Guinea)
Tom Schwarz (England)
Juan Chang (Guatemala)
Gary Ogilvie (England)
Stephen Hoyle (England)
Matt Wiesenfarth (USA)
Colin van Gool (Netherlands)
Sean Morris (USA)