Lawyers for the refugee have asked the High Court to overturn the landmark al-Kateb ruling of 2004.

The court's decision may have implications for more than 50 other refugees with adverse security assessments. Photo: Louie Douvis

A majority of the High Court today held that a decision to refuse a Sri Lankan asylum seeker a protection visa after he received an adverse security assessment by ASIO had not been made according to law.

In a decision that may have implications for more than 50 other refugees with adverse security assessments, the majority held that a regulation which prevented the grant of the protection visa was invalid.

The plaintiff, a Sri Lankan known only as M47, has been in detention since his arrival to Australia three years ago.

A delegate of the Minister for Immigration found that the 36-year-old Tamil, who has a wife and child in Sri Lanka, had a well-founded fear of persecution in Sri Lanka, but refused his application for a protection visa because he had been assessed by ASIO to be a risk to security.

Led by David Manne, the legal team that successfully challenged the government's Malaysian people-swap agreement launched the High Court action on M47's behalf in May, challenging the validity of the decision to refuse him a protection visa and challenging his continued detention.

''This is a significant victory for our client,'' Mr Manne told the National Times.

''The court has held that the processing of his protection visa, which is crucial to his freedom, was unlawful. The only thing that stood between our client, a refugee visa and his freedom was a regulation which the court has ruled is invalid.

''He should urgently be granted a refugee visa and his freedom. The government should now end, not only the detention of our client, but others in a similar predicament.''

The asylum seeker also argued that ASIO had denied him procedural fairness when making a fresh adverse security assessment in 2012 and that the Migration Act did not authorise the removal and detention of a person found to be a refugee.

A majority of the Court held that the plaintiff was not denied procedural fairness in connection with the making of the security assessment because the plaintiff was given the opportunity to address issues of concern to ASIO in the interview that was conducted before the fresh assessment was made in 2012.

However, a majority of the Court held that the migration regulations could not validly prescribe public interest criterion 4002 as a condition for the granting of a protection visa because doing so was inconsistent with the Migration Act.

Accordingly, it ruled that his continuing detention was valid for the purpose of determining his application for a protection visa.

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