Iwi in Nelson have lost a 20-year legal battle for freehold title to an area of mudflats north of the city.
Te Huria Matenga Wakapuaka Trust, backed by Ngati Tama, has been fighting to gain freehold title to the estuary at Delaware Bay.
It was granted the title by the Maori Land Court in 1998, but lost it in a Court of Appeal decision.
On Thursday, the Supreme Court said it could not take a different view from the Court of Appeal and denied the Trust's appeal.
Ngati Tama trust chair Fred Te Miha says the Crown lost documents that would have proved the existence of freehold title from the 19th century.
"We can understand in the early days that there was a lot stolen off us and different legislative acts that took it, but this is modern day. It's another land grab."
Mr Te Miha says iwi may be able to use the new Marine and Coastal Area Act to claim customary title to the mudflats.
He told Waatea News a hui at the weekend will decide Ngati Tama's next step.