It is still unclear if France recognises either of the two kings on Wallis enthroned by rival royal families this month.
The public broadcaster of Wallis and Futuna says the French prefect has written to the two monarchs, asking them to show respect for the legality of their actions.
11 days ago, Tominiko Halagahu was made the new king but a rival council of chiefs enthroned Patalione Kanimoa two days later to fill a two-year vacancy.
A king and the chiefs are part of the territorial administration and on the payroll of the French republic, yet it is not known if any of the new monarchs is being remunerated.
The prefect says he won't interfere in customary matters, urging both camps to find a solution in the general interest.
However, the prefect will be tasked with making the king's installment legal by entering it in the official journal.
The rival council of chiefs has declined to comment on the prefect's letter.