According to an article on the stuff.co.nz site the police arrested the four men suspected of breaking ownership laws with the website Megaupload on an American arrest warrant.
New Zealand is now arresting its own inhabitants and citizens on the say so of a foreign Nation. A Nation which has recently signed into law their ability to detain its own citizens (they already applied this to people of other Nations) indefinitely without trial or court hearings.
Whether they have broken the law or not or whether you support draconian copyright laws or not this sets an incredibly dangerous precedent as the descent into a police state in the US progresses. The next NZ police could arrest on behalf of a the US could very well be those of us who voice dissent.