French Polynesia is under the extradition treaty with France, but most countries reserve the right to not honor extradition if they find the charges are political.
There’s another layer of isolation in that Tetiaroa Island is a private island, surrounded by a large coral reef. There is no real port or even a dock of any scale there, and the airport is tiny, looks like a sand strip cut into the edge of jungle. Two Brando resort owned planes are the only air connection that I can tell. So, who gets in and who gets out is very well controlled. Short of sending an aircraft carrier and launching a chopper, it would be difficult to get any sort of legal or military presence on that island without several hours’ notice.