The Labour Party continues to doubt whether the Government has the right to regulate shipping in waters above the continental shelf - even though it is adamant it does.
A bill amending the month-old Crown Minerals Amendment Act was put though Parliament under urgency at the weekend as part of a Budget legislation package and comes into effect this Friday.
It extends a crackdown on anti-mining protests at sea to areas on or above the continental shelf.
Under the United Nations Convention on the Law of the Sea, coastal states exercise sovereign rights over the continental shelf for the purpose of exploring and exploiting its natural resources.
Labour says they cannot, though, infringe or unjustifiably interfere with navigation.
Energy and Resources Minister Simon Bridges says the Government has the right to regulate the activity of protest boats.
But Labour's energy and resources spokesperson Moana Mackey says if that's the case, Mr Bridges should have answered questions when the bill was being considered during its committee stages.
Ms Mackey said the Ministry of Foreign Affairs and Trade had advised that governments could not legislate activity in the waters above the continental shelf.
Simon Bridges says New Zealand has sovereign rights to enforce in the Exclusive Economic Zone and continental shelf area.
"We have the ability to extract natural resources and also to enforce our rights in relation to that. The law that we have passed is very similar indeed to a law that other countries have passed including Australia."
Mr Bridges says many departments, including the Ministry of Foreign Affairs and Trade, were consulted in the drafting of the bill.
He told Radio New Zealand's Morning Report programme on Monday the law does not take away the right to protest but tackles dangerous behaviour on the high seas.
However, an expert on the international law of the sea has warned that the Government will have to be careful about how it applies the legislation.
Joanna Mossop, a senior law lecturer at Victoria University says while the Government is probably on safe ground, it is a grey area in the law.
Ms Mossop said it's significant the new law makes it clear that no proceedings will be taken against a foreign ship without the approval of the Attorney-General.
"That's usually an indication that there's little intent to apply this to a foreign vessel because of the potential consequences under international law."
Meanwhile, the Green Party has obtained documents under the Official Information Act that confirm New Zealand does not have the capability of dealing with an undersea oil spill.
Energy spokesperson Gareth Hughes says the paper from Maritime New Zealand contradicts statements by Simon Bridges that the country is prepared for an oil spill from a deep sea rig.