The government's Unsolicited Electronic Messages Bill has been reported back [PDF] from committee. I haven't been following this closely, but it seems the committee has tightened up the bill a little and removed the cloak of messages which are merely "promotional" rather than "commercial". Previously, promotional messages were considered a separate category and subjected to lower standards (they were opt-out rather than opt-in). This may have allowed spammers to exploit the confusion between what was commercial and what was "promotional". Now the bill is quite clear: there are only commercial messages, and recipients must expressly opt-in.
Strangely, they've also added a new subsection requiring the enforcement agency to monitor sexually explicit (but not indecent) spam, and report on means to control it in future. I blame Gordon Copeland.
As for whether any of this will work, I doubt it. It may deal with New Zealand spammers, but most are in foreign jurisdictions, and will continue to flood our mailboxes with ads for fake degrees, pirated software, counterfeit viagra, and offers of employment as a professional money-launderer. OTOH, it means that next time I get spam from Genesis Energy (yes, really), then I might be able to do something about it.