Nauru's justice system is without any court of appeal, after the Nauruan Government severed ties with the Australian judicial system.

Key points: Nauruan defendants have been able to seek an appeal with the Australian High Court since the 1970s

Nauruan defendants have been able to seek an appeal with the Australian High Court since the 1970s But in March its Government cited affordability and transparency as a reason to change that

But in March its Government cited affordability and transparency as a reason to change that Nauru's Parliament is yet to vote on the matter, but its Government has already scrapped the treaty with Australia

The move by the Pacific island's Government has left former Opposition MPs involved in highly-politicised cases with no avenue of appeal.

Their lawyers only found out about the change after a chance encounter with senior Nauruan officials on a flight to Brisbane.

The highest court in Nauru is its Supreme Court, but since the 1970s, defendants have been able to seek leave to appeal to the Australian High Court as a final arbiter.

Nauru wants to establish its own Court of Appeal to give the nation greater independence, but its Parliament is yet to vote on the matter.

Last month, the Government cited affordability and transparency as the motivation for change, as well as asserting the nation's sovereignty.

Australian jurist and former resident magistrate of Nauru Peter Law said he believed it was a laudable goal, but described the timing as "alarming".

It "indicates … a political undercurrent to these actions," he said.

That is because the timing affects the case of several former Nauruan MPs who were involved in an ugly protest in 2015.

The protest was, ironically, related to their concerns about the independence of the judiciary.

Nauru Government already scrapped treaty

Two Australian lawyers for the Opposition MPs were on flight from Nauru back to Australia on Good Friday after hearing a judgement on the case.

On the same flight was Nauru's Solicitor-General Jay Udit.

A casual chat on arrival in Brisbane revealed the Nauruan Government had already formally notified Canberra it was scrapping the treaty that allows appeals to be heard by the Australian High Court.

Although the Nauruan Government's intention to set up its own Court of Appeal had been flagged, it had not publicised the formal notification to cut ties with the Australian judicial system.

The ABC understands this took place on the December 12 and that it took effect three months later.

Therefore, as of March 13 appeals to Nauruan Supreme Court decisions can no longer be heard in Australia.

'They no longer have an appeal route'

Given a new Nauruan appellate court has not yet been established, nor approved by Parliament, there are no options for further appeal.

One of the lawyers for the Opposition MPs, Christian Hearn, said it left the defendants "in a state of limbo".

"At this stage, through executive action in a highly politicised case, they have been denied their rights to appeal against the decision of the Supreme Court last week," he said.

"They no longer have an appeal route to the [Australian] High Court and they have no other appeal route."

Mr Hearn said there had been no notification by the Nauruan Government, the public prosecutor or the Supreme Court about the major change in the legal landscape.

'That's unfair'

Mathew Batsiua is one of the former Opposition MPs before the Supreme Court over the 2015 protest.

He spoke to the ABC from Nauru where he is on bail awaiting appeal — an appeal it seems he can no longer pursue.

"Shutting off the avenue of appeal to the High Court … means that we'll be disadvantaged and that's unfair."

Mr Batsuia is also a former justice minister of Nauru.

He states it is the Nauruan Parliament — not the Government — that has the authority to manage treaties with Australia.

He has accused the Nauruan Government of acting beyond its powers by revoking the appeal avenue.

"There is a rule of law question here, where the parliamentary process seems to have been bypassed by the Government."

There are concerns the change could affect asylum seekers. ( Department of Immigration and Citizenship )

Mr Law is similarly concerned that the executive has acted beyond its powers.

"The history of the last four years suggests to me the Government has no real understanding of the rule of law and the separation of powers," he said.

"The way that decisions have been interfered with — or commented on — by Parliamentarians ... and the fact that orders of the [Supreme] Court have been ignored leads me to think that Justices may feel pressured by the Parliament in their decision making."

Change a serious matter for asylum seekers

Many of the appeals to Nauruan Supreme Court decisions that reach the Australian High Court have been cases involving asylum seekers.

Prominent lawyer and advocate George Newhouse described the change as a very serious matter for asylum seekers on Nauru.

"When the High Court has a record of overturning eight out of 11 adverse decisions by the Nauruan courts against asylum seekers, it really is very important that those asylum seekers have an independent court they can appeal to," Mr Newhouse said.

Australia is Nauru's largest foreign aid donor and works closely with the Nauruan Government on the arrangement for the Pacific nation to process asylum seekers wanting to come to Australia.

Australia supports Nauru's sovereignty, according to a statement by Julie Bishop. ( ABC News: Adam Kennedy )

In a statement, Foreign Minister Julie Bishop said "Australia supports Nauru's sovereignty and its December 2017 decision to terminate the treaty in advance of the nation's 50th anniversary of independence".

Mr Batsiua believes the Australian Government should be questioning the Nauruan Government's decision and its timing.

So does Mr Law: "It reflects poorly on Australia as well, because we're associating our Government with another Government which displays all the hallmarks of a rogue regime."

The Nauruan Government has been contacted for comment.