A bid by Greenpeace to have Anadarko's deepsea oil drilling permit declared unlawful has failed.
A High Court judge in Wellington has dismissed an application by the group for a judicial review of how the environmental effects of drilling in the Taranaki Basin were assessed.
The drilling started in November this year.
Greenpeace argued that the Environmental Protection Authority was wrong to have accepted an incomplete impact assessment from Anadarko.
But Justice MacKenzie said the decision was for the authority and it was properly taken.
Greenpeace said the High Court decision confirms that regulation of deepsea drilling is a farce.
The EPA said in a statement it was pleased with the findings.