High Court Rejects Novel Commonwealth Defence To Unlawful Immigration Detention

In Abdel-Hady v Commonwealth of Australia [2026] HCA 17, the High Court unanimously rejected a novel defence advanced by the Commonwealth to a claim for false imprisonment arising from immigration detention later found to be unlawful. The decision is a significant reaffirmation of executive accountability and the rule of law.

Background

Safwat Abdel-Hady, an Austrian citizen, had been held in immigration detention since 2017 following the cancellation of his visa. By 28 July 2022, his medical condition meant there was no real prospect of his removal from Australia becoming practicable in the reasonably foreseeable future. Nevertheless, he remained detained.

At the time, detention in those circumstances was generally understood to be authorised by Al-Kateb v Godwin (2004). That position changed in NZYQ v Minister for Immigration, Citizenship and Multicultural Affairs (2023), when the High Court reopened and overruled Al-Kateb. The Court held that ss 189(1) and 196(1) of the Migration Act 1958 (Cth) could not validly authorise detention where there was no real prospect of removal in the reasonably foreseeable future. As a result, Mr Abdel-Hady’s detention from 28 July 2022 was not authorised by those provisions.

The Commonwealth’s Argument

The Commonwealth accepted that the elements of false imprisonment were otherwise established but argued for recognition of a new, and novel, common law defence. It contended that officers should not be liable where they acted in accordance with binding High Court authority that was only later overturned.

The argument relied heavily on Queensland v Stradford (a pseudonym) (2025), where the High Court recognised protection for officials executing court orders later found to be invalid. The Commonwealth argued that a similar protection should apply to officers acting under legislation previously upheld by the High Court.

The Decision

The Court unanimously rejected the proposed defence.

A central feature of the reasoning was that NZYQ did not change the law prospectively; it declared what the law had always been. Accordingly, the relevant provisions were invalid in their application to persons whose removal had no real prospect of becoming practicable in the reasonably foreseeable future. They therefore never validly authorised Mr Abdel-Hady’s detention.

The Court also rejected the analogy with Stradford. The protection recognised in that case was tied to judicial orders and the need to preserve judicial authority and independence. Immigration officers were not enforcing court orders but acting under legislation later found not to authorise the detention in question.

Implications

The decision confirms that constitutional rulings generally operate retrospectively and that governments cannot avoid liability simply because they acted in accordance with an earlier judicial interpretation later overruled.

It also reinforces the principle that executive action affecting personal liberty must ultimately be supported by lawful authority. A mistaken understanding of the law, even one based on an earlier High Court decision, is not itself a defence to unlawful detention.

While Abdel-Hady does not itself determine entitlement to damages, it removes a significant defence previously advanced by the Commonwealth and is likely to strengthen claims by persons detained in circumstances analogous to NZYQ.

Conclusion

Abdel-Hady confirms that where detention is ultimately found never to have been lawfully authorised, compliance with a previously accepted understanding of the law does not provide a defence to false imprisonment. The decision is a powerful statement of the rule of law and executive accountability.

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