The full bench of the High Court found that errors of law had been made because those reviewing the men's claims failed to treat Australian law as binding and failed to observe the requirements of procedural fairness.

Allens Arthur Robinson partner Malcolm Stephens, who led the team on the pro bono matter, said the impact of the decision went beyond the two men involved.

"Today's decision will allow our clients, and those in similar situations, to have their claims for refugee status assessed in accordance with Australian law, including the requirement to afford procedural fairness," said Stephens.

"This is a basic right that had been denied to those asylum seekers who entered Australia outside the migration zone."

Stephens also said the judgment will mean that decisions made under the offshore processing system can be reviewed by the courts.

"The High Court held that our client's case was not handled fairly or lawfully. Our expectation is that his application will now be heard again in accordance with law," said Stephens.

Given the full bench of the High Court had heard the case in the first instance highlighted the importance of the legal issues being debated, according to Allens senior associate Alexia Mayer, who also worked on the case.

"At the heart of this case was the fundamentally important question of whether decisions made under the offshore processing regime, which can affect the liberty - and potentially the lives - of asylum seekers, and which attract Australia's obligations under the Refugees Convention, must also be lawful and subject to judicial supervision," she said.

Allens was asked to take the case by the Refugee Immigration and Legal Centre and worked with barrister Debbie Mortimer SC on the matter. Holding Redlich also acted on the matter.