Government Liability for False Imprisonment: Relying on Past Reasoning from the High Court is No Excuse

Ellen Rock

19.6.2026

When the High Court of Australia handed down its seminal judgment in NZYQ v Minister for Immigration, Citizenship and Multicultural Affairs (2023) 280 CLR 137 (NZYQ) in 2023, one of the anticipated consequences was that it would open the door to a raft of potential false imprisonment claims from individuals who (as it turns out) had been unlawfully held in immigration detention. A large step forward has now been taken towards that possibility, with the High Court refusing to recognise a novel common law defence that would have protected the Commonwealth from liability in Abdel-Hady v Commonwealth [2026] HCA 17 (Abdel-Hady).

The history and implications of NZYQ are well-known. By way of brief recap, in 2004 the High Court had ruled on the constitutional validity of key provisions in the Migration Act 1958 (Cth) (Migration Act) that give effect to mandatory immigration detention. For nearly 20 years, Al-Kateb v Godwin (2004) 219 CLR 562 (Al-Kateb) stood for the proposition that ss 189 and 196 of the Migration Act validly authorised the ongoing detention of an unlawful non-citizen, even if there was no real prospect of them being removed from Australia under s 198 in the reasonably foreseeable future.

This includes individuals who the government wants to remove (perhaps because their visa has been cancelled due to criminal conduct), but who have nowhere else to go, or who no other country is willing to accept. For that group, the Migration Act essentially authorised indefinite detention.

In NZYQ, the High Court reopened and overruled the constitutional holding in Al-Kateb on the basis that applying the Migration Act powers to people in this category is inconsistent with Chapter III of the Constitution. The Court has also ruled against subsequent regulatory workarounds in YBFZ v Minister for Immigration, Citizenship and Multicultural Affairs (2024) 419 ALR 457 and EGH19 v Commonwealth [2026] HCA 7. The reasoning underpinning those cases has been explored in detail elsewhere. This post is concerned with the liability implications arising from these findings.

The law of false imprisonment

The upshot of NZYQ and later cases is that the government has for some time been relying on an invalid law to detain unlawful non-citizens where there is no foreseeable prospect of removing them from Australia. There is a clear connection here to the tort of false imprisonment, which is concerned with situations where a person (including a government official) detains a person without lawful authority to do so.

The false imprisonment tort is designed to compensate a person for ‘injury to liberty’ (Kirby J in Ruddock v Taylor (2005) 222 CLR 612 at [141] (Ruddock)). There are two key ingredients to establish liability – detention and lack of lawful authority. The burden of proving each of these elements is split between the parties: the plaintiff is responsible for showing that they have been detained, after which the defendant needs to justify the act of detention by reference to lawful authority ‘if he could’ (Trobridge v Hardy (1955) 94 CLR 147 at 152–3).

It seems clear that individuals held in immigration detention facilities would fall within the legal meaning of ‘detention’ for the purpose of this tort. The more difficult question is whether or not that detention was authorised. In theory, Al-Kateb suggested that the Migration Act legally authorised immigration officials to detain and hold unlawful non-citizens in immigration detention irrespective of whether there was a foreseeable prospect of removal.

The High Court’s judgment in NZYQ effectively pulled that rug out from under the Commonwealth in 2023. Because a ruling on the invalidity of a law operates retrospectively, the statutory provisions ‘must be taken always to have been invalid’ insofar as they applied to individuals who had no foreseeable prospect of being removed (at [5]).

If the Commonwealth could not rely on ss 189 and 196 as a source of lawful authority, this gave rise to a spectre of potential liability for false imprisonment. This was one of the concerns that the Commonwealth had raised in argument before the High Court ahead of the outcome of NZYQ. That prospect has since been realised, with a number of claims of false imprisonment being commenced by individuals falling within this class.

Abdel-Hady’s proceedings

Mr Abdel-Hady first came to Australia from Austria in 1997. He lived here as a visa-holder for 20 years, when his then-current visa was cancelled by the Minister on character grounds (pursuant to s 501(2) of the Migration Act). From 2017 he was held in immigration detention pending his removal from Australia.

In 2021, Mr Abdel-Hady commenced proceedings in the High Court, seeking judicial review remedies to address the legality of his detention and damages for false imprisonment. The judicial review aspects of the claim were remitted to the Federal Circuit and Family Court of Australia (FCFCOA).

While those judicial review proceedings were pending, it became clear that there was no realistic prospect of deporting Mr Abdel-Hady. This was due to a health condition that restricted his ability to travel. The Commonwealth agrees that this was likely the case from at least July 2022, meaning that Mr Abdel-Hady can be taken to fall within the NZYQ cohort from that date. Once the Commonwealth came to accept this reality in 2024, it consented to orders in the FCFCOA declaring that Mr Abdel-Hady’s continued detention was unlawful and he was released.

With the illegality of his detention now confirmed, it remained necessary for the High Court to address the balance of the false imprisonment claim. With other similar cases pending in the courts, the parties agreed to present a narrow legal question to the High Court about the Commonwealth’s liability as a ‘test case’. This test case was focussed on whether the Court should recognise a new common law defence that would protect the Commonwealth from liability.

Defence of lawful imprisonment

The law recognises a limited range of defences to liability for false imprisonment, such as consent and necessity. Perhaps the most obvious defence is the one that’s built into the structure of the tort itself – the existence of lawful authority to detain. A defendant can avoid liability by pointing to a specific form of power to detain, such as a statutory power authorising detention, or a warrant of arrest or imprisonment. The power contained in s 189 of the Migration Act is an example, authorising (or more accurately requiring) immigration officers to detain a person that they reasonably suspect is an unlawful non-citizen.

There are a number of different ways that questions about lawful authority can arise in a false imprisonment claim. One of the simpler scenarios is where it is unclear whether or not a defendant has properly engaged the detention power. Thus, liability might arise where a defendant holds a person in detention for longer than the maximum period contemplated by a statutory power. In those types of cases, a valid form of authority to detain exists, but does not protect the defendant in the circumstances.

Things become much more complicated where it turns out that there is a legal flaw in the source of authority itself (eg, in the statutory power, warrant etc). There are a few different ways that this might happen, and as I have explained in more detail elsewhere, liability outcomes will depend on the location of the flaw and who is responsible for it. A few examples paint a picture of these complications.

In Ruddock, immigration officers had relied on the detention power in s 189 of the Migration Act to detain Mr Taylor, who had apparently become an unlawful non-citizen when his visa was cancelled. As it turns out, the visa cancellation decision was invalid on administrative law grounds amounting to jurisdictional error. Because an administrative decision flawed by jurisdictional error is ‘no decision at all’, from a legal perspective it was incapable of having turned Mr Taylor into an unlawful non-citizen. This brought the legality of his detention into question.

On appeal, the High Court ruled that the detention was lawful despite the flawed visa cancellation decision. This is because s 189 imposes a duty to detain where an officer reasonably suspects a person is an unlawful non-citizen, and ‘what were reasonable grounds for effecting the respondent’s detention did not retrospectively cease to be reasonable’ when the cancellation decision was later quashed (at [40]).

This can be contrasted with the positive finding of liability in Commonwealth v Okwume [2018] FCAFC 69, which also involved detention under s 189. In that case, the officer exercising the detention power was also the author of the invalid decision to cancel the plaintiff’s visa, and therefore was in a better position to be on notice of the potential infirmity of that decision (at [137]).

Different considerations arise when the author of the flawed instrument is a judge. New South Wales v Kable (2013) 252 CLR 118 (Kable (No 2)) remains a leading authority on that point. Mr Kable had been imprisoned pursuant to a court order that had been made under legislation that was later held to be constitutionally invalid (see Kable v Director of Public Prosecutions (1996) 189 CLR 51).

Because invalid legislation is ‘no law at all’ (Kable (No 2) at [51]]), Mr Kable sought damages for false imprisonment. The High Court found against Mr Kable on the basis that the authority for his detention stemmed from the court order rather than the invalid legislation. Unlike the Minister’s visa cancellation decision in Ruddock, an order of a superior court is valid until set aside, which remains the case even if the order is made pursuant to a constitutionally invalid law (at [32]).

This reasoning was extended slightly further in Queensland vStradford(a pseudonym) (2025) 421 ALR 376 (Stradford). The plaintiff had been imprisoned pursuant to a court order made by a judge of the Federal Circuit Court of Australia (an inferior court) that was later found to have been unlawful. A majority of the High Court confirmed that as an inferior court, Judge Vasta’s orders were retrospectively invalid (at [53], cf Edelman J at [227] and Steward J at [325]). However, the judge was protected by judicial immunity (at [112]), and those giving effect to the order likewise enjoyed a common law defence (at [149]), later described by Gordon J as a ‘derivative defence’ in Abdel-Hady (at [193]).

None of these types of principles offered a direct answer to the situation in Abdel-Hady. Unlike in Ruddock,the legal flaw was not located in an administrative decision, but in the statutory power itself. And there was no court order that might operate as a mediary between the invalid law and the act of detention as in Kable (No 2), or to support an immunity of the type recognised in Stradford.

Immigration officers were instead exercising a statutory power that was itself flawed on constitutional grounds insofar as it applies to the NZYQ cohort. Because an invalid law is ‘no law at all’, it therefore could not be relied on by the government to argue that Mr Abdel-Hady’s detention was legally authorised.

A novel defence

This is where the Commonwealth’s novel defence comes in. Relying on Stradford, the Commonwealth argued that the High Court should recognise a new form of defence that would protect a government official who is carrying out a duty to enforce an apparently valid law that later turns out to have been invalid. It was suggested that this was analogous to protecting officers who give effect to invalid court orders as in Stradford.

The defence was narrowly framed for the present context to apply where the plaintiff was detained:

(i) by an officer of the Executive Government whose duty to obey the law as declared by this Court was reinforced by the Public Service Act [1999 (Cth)]; (ii) acting pursuant to an apparent statutory duty to detain; and (iii) during a period of time when current and binding authority of this Court held that the duty to detain validly applied to require such detention (Gordon J at [102]; see also Gageler CJ, Gleeson and Beech-Jones JJ at [19]).

If recognised, the defence would protect officials who had been exercising detention powers under the Migration Act during the 20-year period that Al-Kateb held sway. It would also protect the Commonwealth, which accepted that it was vicariously liable for the actions of its officers (at [18]). The Commonwealth disputed that it would be directly liable for the detention, but accepted that if the defence was unavailable to its officers, it would also be unavailable to the Commonwealth (at [18]; as to direct liability, see Edelman J at [144]).

All seven judges refused to recognise any such defence.

One difficulty was the artificial framing of the defence around the above criteria (Gageler CJ, Gleeson and Beech-Jones JJ at [28], Gordon J at [107], Edelman J at [149] and Jagot J at [226]). For example, why should the defence be limited to false imprisonment (and not other torts), or to decisions of the High Court (as opposed to other courts), or to statutory duties (as opposed to powers) (Edelman J at [149])? Recognising such a defence was thought to be a potential ‘“foot in the door” to a far more wide-ranging defence’ with broader implications (Gordon J at [108]).

A second difficulty was that the defence was not actually supported by the reasoning in Stradford. That case was concerned with the enforcement of invalid court orders. One of the main reasons offered for the protection was to preserve ‘the authority of judicial proceedings’ (Gageler CJ, Gleeson and Beech-Jones JJ at [43], citing Stradford at [149]), supporting important aspects of judicial independence and impartiality (Jagot J at [208]).

To extend this protection to officers who rely on guidance from past judicial reasoning on the meaning of a statute is an entirely different proposition, and would ‘purport to confer on this Court's reasons or conclusions an authority they do not possess’ (Gageler CJ, Gleeson and Beech-Jones JJ at [44]). As Edelman J observed (at [148]), it is always incumbent on the executive to ascertain and comply with the law on a case-by-case basis, because the legal norms established by previous cases do not bind directly.

The more problematic aspect of the proposed defence was its inconsistency with constitutional principle. The executive enjoys no power to interfere with legal rights and interests except to the extent authorised by law. As stated by Gageler CJ, Gleeson and Beech-Jones JJ, it is the ‘constitutional responsibility of the executive branch of government to ascertain and comply with the law that limits its power’ (at [31]). Likewise, it is a hallmark of judicial power that a ruling about the meaning of the law can later be overruled, with retrospective effect (Gageler CJ, Gleeson and Beech-Jones JJ at [39], Gordon J at [83]–[84]; Jagot J at [217]).

What the Commonwealth was effectively arguing for was permission to enforce a purported (but invalid) law so long as that law had been given a previous tick of approval by the High Court. In argument the Commonwealth described the obligation in terms of a ‘deeper duty’ to comply with the law as declared by the courts (Gordon J at [86]).

In place of a constitutional responsibility to ascertain and comply with the law, the High Court was concerned that this would instead grant the executive an immunity from liability where power has been exceeded. That ‘would amount to an inversion, if not a perversion, of constitutional principle’ (Gageler CJ, Gleeson and Beech-Jones JJ at [34]).

Practical implications

Abdel-Hady was a special case stated to resolve a narrow legal question regarding the novel defence. This still leaves the balance of Mr Abdel-Hady’s tort claim unresolved, though he already has the benefit of the FCFCOA’s 2024 declaration that his detention was unlawful. Whether the balance of the matter will be adjudicated or settled remains to be seen.

It is unclear how many individuals are likely to have a potential claim against the Commonwealth. Reports suggest that around 350 people were released from detention in connection with the NZYQ ruling. It is quite possible that others might also be able to argue that they have previously been detained at a time when the government had no realistic prospect of removing them. Limitation periods will likely stand in the way of some cases.

Assuming some or all of those individuals do bring proceedings, it is not a given that all will be found to have been falsely imprisoned, or that imprisonment was unlawful for the entirety of its duration. For example, the Commonwealth may be able to show that there were reasonable prospects of a person being removed for some or all of the detention period.

However, with the government bearing the onus of proof to establish lawful authority to detain, it will fall to the Commonwealth to produce evidence regarding the prospects of deportation. In practice, that might require the Commonwealth to assemble a ‘retrospective record’ going back a number of years. As the then Commonwealth Solicitor-General noted in argument ahead of NZYQ, that type of record could be maintained going forward, but assembling relevant records going backwards is a more difficult proposition.

For those cases where liability is made out, the scale of compensation is likely to vary considerably between individuals, taking into account factors such as the duration of the imprisonment, the conditions of imprisonment and its impacts.

By way of example, prior to being overturned by the High Court on appeal, Mr Taylor was awarded $116,000 in his immigration detention false imprisonment claim. This took into account the length of his imprisonment (316 days), the fact that he was held in prison rather than immigration detention due to his history of offences against children, as well as impacts to his mental health (Taylor v Ruddock (District Court of New South Wales, Murrell J, 18 December 2002)).

In contrast, it is sometimes possible that the court will award only nominal damages of $1 where it is shown that that detention was inevitable.

Conclusion

The Abdel-Hady case demonstrates the practical difficulties that can arise where the government relies on an invalid source of power to act. Putting court orders to one side, invalidity is generally retrospective, meaning that a person who thought they were covered by lawful authority might later discover it is illusory when they seek to rely on it in court.

One can have some sympathy for an official in these circumstances. This is particularly so when an official is relying on a judgment of the court which seems to suggest that their source of authority is sound. As the House of Lords observed in R v Governor of Brockhill Prison; Ex parte Evans [2001] 2 AC 19 at 26, a governor who relies on common law guidance on the meaning of a statutory detention provision can hardly be criticised for doing so—‘what more could he have done?’

Whatever sympathy we might have for individuals exposed to liability, the High Court in Abdel-Hady confirmed that it does not justify an approach that would allow an invalid law to cloak the government in lawful authority when carrying out acts that infringe the liberty of the individual. As Gordon J observed (at [95]), this would have the effect of shifting the burden of unfairness from the government to the individual.

To the extent that these examples of unfairness are of concern to government, it remains possible for Parliament to establish good faith protections that limit personal liability (an example being s 198(13) of the Migration Act). More generally, it emphasises the potential risks of setting up legislative regimes that depend on the conferral of wide-ranging detention powers on the executive.

Ellen Rock is an Associate Professor at the UNSW Faculty of Law and Justice, and co-Director of the Administrative Law and Justice Project in the G+T Centre of Public Law.

Suggested citation: Ellen Rock, ‘Government Liability for False Imprisonment: Relying on Past Reasoning from the High Court is No Excuse’ (19 June 2026) <https://www.auspublaw.org/blog/2026/6/government-liability-for-false-imprisonment-relying-on-past-reasoning-from-the-high-court-is-no-excuse>