The iwi and some residents around Kaipara Harbour have placed a rahui or customary ban over the harbour in protest against 200 Crest Energy tidal turbines going ahead.
The protest is being led by the Kaipara Harbour Rahui Action Committee, set up by the Te Uri o Hau Settlement Trust.
The trust fought against the original application through the Northland Regional Council, and then the Environment Court, before Crest Energy was granted resource consent in March 2011.
It says about 150 iwi members and locals gathered at a rahui ceremony over the weekend at Pouto Point.
An iwi member and committee spokesperson, Mikaera Miru, says the iwi considered the resource consent application process as being the last safeguard to protect their marine environment.
He feels the Crown has subverted justice in issuing the consent.
He says Maori in particular look to the resource consent process as being a legal tool to allow them to have a say about the protection of resources in their communities.
Mr Miru says local and central government including the Environment Court have all undermined that process in order to run amok on the resources in their rohe.
A rahui makes an area tapu or off-limits either in order to conserve kaimoana stocks or to avoid contamination that could make seafood unsafe to eat.
In this case, Te Uri o Hau is using a rahui to restrict Crest Energy's access to the harbour because of environmental concerns, such as fish getting caught in the turbines.