By Phil Mercer
BBC correspondent in Sydney
A group of men convicted of sexual assaults on Britain's South Pacific territory of Pitcairn have begun a challenge against conviction.
Pitcairn mayor Steve Christian was sacked after being convicted of rape
The men claim they did not realise they were subject to English law on the remote island.
Four islanders were last year given jail sentences but remain free pending hearings challenging their convictions for sexually assaulting young girls.
Two other Pitcairn men were given non-custodial sentences.
Those due to be jailed were given prison sentences ranging from two to six years.
Defence lawyers are expected to argue that legislation covering serious offences was not properly introduced or promulgated by British officials
The first of two hearings will be heard by the Pitcairn Supreme Court which is sitting in special session in New Zealand.
Preliminary proceedings are under way.
Defence lawyers are expected to argue that legislation covering serious offences was not properly introduced or promulgated by British officials. The UK regards Pitcairn as its last remaining overseas territory in the South Pacific.
It is administered by diplomats based in New Zealand.
They have said the island is governed by a series of local Pitcairn ordinances which are complemented by English laws for offences such as rape and murder.
The diplomats have insisted that the correct legal procedures have always been followed.
Many islanders have never accepted British rule over Pitcairn.
The rocky outcrop was settled in 1790 by mutineers who seized control of HMS Bounty and were on the run from the authorities.
A challenge to Britain's sovereignty over the island will be the subject of a separate hearing before the privy council in London, expected to take place later this year.
Five more former Pitcairn islanders have been charged with sexual abuse and will face court in the coming months.