As reported the NZ Herald is not blocking access to old stories (it is to new opionion articles though), it has merely made its internal search engine generate links which require paid access. One can use Google search engine to get around this.
A clever chap or chapette invented a little script which will take the NZ Herald internal search engine link and transform it to a direct free link. This appears to be legal because the NZ Herald has decided to make both links available – it merely finds them for you.
As with most Net wars, the NZ Herald has moved to plug this loophole, but the author is promising a second version which will use a different method.