The high court has ruled the Migration Act does not prevent asylum seekers transiting through Australia from suing the commonwealth for negligence including failure to provide medical care.
The unanimous ruling on Wednesday deals a major blow to an attempt by the home affairs minister, Peter Dutton, to avoid commonwealth liability in 50 federal court cases brought by asylum seekers and refugees.
George Newhouse, the director of the National Justice Project which led the test case, told Guardian Australia the result meant the government’s “attempts to delay or deny justice to these vulnerable asylum seekers has failed”.
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After coming to Australia temporarily for care, the four asylum seekers party to the case sued the commonwealth in the federal court for breaching a duty of care to provide them healthcare in the regional processing centre on Nauru.
The parties include DLZ18, a child who the justice project argued was owed “urgent paediatric physical and psychiatric care” and DIZ18, who needed “an MRI head scan and specialist paediatric treatment”.
Newhouse said the children had suffered from Australia’s “cruel” offshore detention policies and had “constant nightmares”, struggled to interact with other children, and experienced suicidal thoughts. “Some of them have self-harmed or attempted to take their own lives,” he said.
The home affairs minister had sought to block the cases by arguing the Migration Act stated that certain proceedings – including those relating to “transitory persons” – “may not be instituted or continued in any court”.
The full federal court interpreted the section to mean that its jurisdiction to hear the cases was limited and they could only be raised in the high court.
But in Wednesday’s unanimous decision, five judges of the high court ruled the Act “does not limit the jurisdiction of any court”. The section explicitly preserves the high court’s jurisdiction to hear migration cases and did not explicitly state that courts other than the high court have no jurisdiction, they said.
The justices said the section was “a bar to a remedy, rather than a limitation on jurisdiction”. Instead of blocking the federal court from hearing the cases, the section “creates a defence” which the commonwealth will need to prove applies in each case.
The judges concluded the most workable interpretation was that both courts could hear the cases, or else the high court would become a “post box for the commencement of proceedings destined to be remitted to another court”.
Allowing the federal court to hear them would avoid “diverting” the high court from its other work and the “administrative inconveniences” of starting cases in the high court – for which the commonwealth “could not identify any purpose or utility”.
Despite conceding the section could operate as a defence, the high court held it “does not exclude all common law negligence cases against the commonwealth” – a positive sign for the four asylum seekers when their matters return to the federal court.
Asylum seekers may also seek to challenge the exercise of government powers and the validity and scope of the Migration Act, the high court said.
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Newhouse said the decision “vindicates the right of our clients to seek justice for the cruel and inhumane treatment they suffered”.
The lawyer said Dutton’s attempt to claim there was no jurisdiction had caused a “very serious problem” for the 50 related cases “every one of which has been held up pending this decision”.
“Justice delayed is justice denied to these individuals,” Newhouse said. “We’re hoping the government will act as model litigants and not take arcane points in the remaining matters.”
Guardian Australia contacted Dutton for comment. The home affairs department replied on his behalf that it was aware of the judgment and was considering the court’s reasons.
“The department is aware there are other ongoing litigation matters that may be affected by the judgment,” a spokesperson said. “It would not be appropriate to comment on any ongoing matters that are currently before the court.”