Conservation Minister Eugenie Sage says she wants to ban the sale of all moa bones.
It comes amid pressure from conservationists who are demanding Trade Me stop allowing the bones to be listed.
However, the website says it will only act if the law changes.
A bone 23 centimetres long and 13 centimetres wide, advertised as a moa foot, could be all yours from TradeMe.
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"As soon as there's a trade, there's an incentive to start illegally collecting them, chopping up the bones cause you get more money that way," said museum curator Mike Dickison.
The problem is a loophole in the law. Native species are protected from sales, but extinct animals are different.
Unless they're found on DOC land or archaeological sites, they're fair game.
"It just makes it super easy to flog off illegal bones since Trade Me doesn't actually verify the authenticity, or legality of that sale," said Dickison.
Another problem is thieves.
"People are taking them illegally, some of the caves are in remote areas, so they can't be monitored all the time," says Sage.
The Conservation Minister says extra security has been installed around some caves.
It's also in place on archaeological sites. Eugenie Sage says it's just easier to ban the sales.
"There is a power under the wildlife act to prohibit the sale of moa bones and moa eggs," she said.
First, she's waiting for a discussion document from DOC. And her cabinet colleagues would have to support it.
Until then, they'll remain online too.
Trade Me says if bones like these weren't sold on its site, they would be sold elsewhere. It adds there have only been around 10 listings for moa bones in the last year.
It's even suggesting there's no appetite for a ban.
"We've not had a lot of complaints though in fact, we've only had three and in the context of eight million live users, that's a really small number," said Trade Me's head of trust and safety George Hiotakis.
Trade Me says it will also use experts to help verify sales if it's unsure. The Conservation Minister says the bones are incredibly useful for research and shouldn't be sold.
Any law change could be months away, but until then, they'll stay online.