France's highest administrative court says the constitution would have to be changed to allow for New Caledonia's indigenous people to be automatically enrolled for next year's independence referendum.
The clarification has come at the behest of the French prime minister Edouard Philippe who is due to host New Caledonian leaders within weeks to finalise preparations for the plebiscite.
The court's advice was that indigenous voters need to first be on the general roll before they can be listed on the restricted roll for the referendum.
The court's view has been communicated to the political leaders in New Caledonia.
Mr Philippe is urging them to meet under the auspices of the French High Commission to prepare for the final Paris meeting of the signatories to the Noumea Accord.
He said they should approach the work ahead with responsibility and wisdom.
In a first response, the anti-independence Caledonian Republicans noted that there was no obstacle to enrolling everybody on the general roll.