The Government says it is open to a deal with iwi on the proposed Kermadec Islands marine sanctuary.
But it wants any promise by iwi not to fish in the sanctuary to be signed into law, rather than simply taking them at their word.
The Government has delayed the creation of the 620,000sq km sanctuary around the Kermedecs until a dispute over Maori fishing rights is resolved.
Te Ohu Kaimoana, which represents Maori fishing interests, says the sanctuary breaches its Treaty rights.
Its leaders have proposed to Government a compromise in which its rights are preserved, but Maori fisheries voluntarily agree not to fish in the region for a period of time.
Environment Minister Nick Smith said today that he was open to this approach.
But he was not comfortable with a voluntary rahui, or ban on fishing, and would want any agreement not to fish to be written into law.
Without this safeguard, there would be no legal recourse for the Government if fishing vessels chose to flout the sanctuary and fish there in future, he said.
"The option we were not prepared to accept is an option that excluded New Zealand quota holders from being able to fish in the area, in which we had no more than a letter on behalf of [Te Ohu] that said they would not fish in 10 years' time, and a piece of law that specifically exempted [Te Ohu] from the prohibition on fishing in the sanctuary."
Smith also said it would be unfair to remove the quota of non-Maori fishing companies which had fished in the region, while not removing the quota of iwi who had not fished there.
Five companies have utilised their fishing quota in the Kermadec Islands region in the past 20 years, and none of them were Maori, he said.
Maori Party co-leader Marama Fox agreed that any agreement between Crown and iwi over the Kermadecs would need to be written into law.
She suggested that the legislation governing the sanctuary could then be reviewed after 10 years, instead of 25 years as proposed by the Government.
The Maori Party has not ruled out severing ties with National over the Kermadecs issue, which some iwi leaders have compared to the foreshore and seabed debate.
It plans to meet with Te Ohu next week before taking their concerns to Government ministers.
Prime Minister John Key personally called the co-leaders yesterday to restart negotiations on the matter.