Finnian Clarke: Habeas Corpus and the Nature of “Nullity” in UK Public Law


In the case of The UK Withdrawal from the European Union (Legal Continuity) (Scotland) Bill – A Reference by the Attorney General and the Advocate General for Scotland, the Supreme Court briefly directed its focus to its understanding of the nature of “nullity” following a finding of administrative unlawfulness. Its approach surprised some commentators, but in this post I will suggest that, far from being completely novel, the distinctions it appears to draw are familiar within the law of habeas corpus. This comparison will, I suggest, cast light upon the shifting and somewhat complex idea of “nullity” in UK public law.

Habeas corpus and judicial review

One controversial topic in habeas corpus law concerns the availability of the writ in cases where judicial review might also offer a remedy. In summary, where an administrative or judicial act authorising imprisonment is impugned, the remedy of judicial review takes primacy, unless the error rendering the authorisation unlawful is outside the jurisdiction of the decision-maker. Parties bringing a habeas corpus action against an authorisation that appears on its face to be within the jurisdiction of the decision-maker will be told in effect to wait until that act has been struck down via judicial review. If then they are still not released, the writ of habeas corpus will issue. An authoritative statement of this principle was advanced by Lord Donaldson MR in R v Secretary of State for the Home Department ex p. Cheblak [1991] 1 WLR 890 at 894C-E where he stated that:

“A writ of habeas corpus will issue where someone is detained without any authority or the purported authority is beyond the powers of the person authorising the detention and so is unlawful.  The remedy of judicial review is available where the decision or action sought to be impugned is within the powers of the person taking it but, due to procedural error, a misappreciation of the law, a failure to take account of relevant matters, a taking account of irrelevant matters or the fundamental unreasonableness of the decision or action, it should never have been taken.  In such a case the decision or action is lawful, unless and until it is set aside by a court of competent jurisdiction.  In the case of detention, if the warrant or underlying decision to deport, were set aside but the detention continued, a writ of habeas corpus would issue.”

To paraphrase, Lord Donaldson MR states that, where a legal authorisation for imprisonment is defective due to an error going to jurisdiction (“a jurisdictional error”), the remedy of habeas corpus is available. However, where that authorisation is on its face lawful (but later found to be defective due to some public law error, i.e. “a non-jurisdictional error”), judicial review takes remedial primacy. This distinction has been discussed in Sharpe and Farbey’s “The Law of Habeas Corpus” 3rd ed., in which the authors argue that such a formulation is inconsistent with the line of authority stretching back centuries and encompassing the House of Lords decisions of R v Governor of Brixton Prison, ex p. Armah [1968] AC 192 and R v Secretary of State for the Home Department, Ex parte Khawaja [1982] 1 WLR 625 (page 58), which emphasised that, in cases concerning the liberty of the individual, hearings ought to take priority in the court list and remedies should be afforded as a matter of right, as in habeas corpus proceedings (see pages 56-63).

Nevertheless, this distinction has been upheld in numerous authorities, even after ex parte Page illuminated our understanding of jurisdiction, including in R v Secretary of State of State for the Home Department, ex p. Muboyayi [1992] 1 QB 244, R v Oldham Justices ex p Cawley [1997] 1 QB 1, and most recently in Guy Jane v City of Westminster Magistrates’ Court (granted leave to appeal to the CA) at para. 47. The principle applies whether the act of authorisation is administrative or judicial in origin. The recent upholding of these principles is important for present purposes in that it highlights a contrast between the remedial consequences of administrative acts that disclose jurisdictional errors of law, and those which disclose non-jurisdictional errors. Where the administrative decision authorising imprisonment is alleged to contain errors made within the jurisdiction of the decision-maker, the appropriate remedy will come via judicial review, which is inherently discretionary. In cases in which the administrative decision authorising imprisonment is alleged to contain errors outwith jurisdiction, the appropriate remedy will be granted by the writ of habeas corpus, which issues as of right and is non-discretionary. It will be submitted below that the operation of this distinction tells us something about the different shades of administrative unlawfulness that can be allocated to an administrative act.

How does this affect the way we think about administrative unlawfulness?

The standard theory of administrative unlawfulness is that, as Wade and Forsyth put it at page 247 of “Administrative Law”, 11th ed., an unlawful administrative act is “a nullity, utterly without existence or effect in law …. Errors such as bad faith, wrong grounds, and breach of natural justice all necessarily involve excess of jurisdiction and therefore nullity”. As Adams frames it in “The Standard Theory of Administrative Unlawfulness” CLJ 2017, 76(2), 289-310, 291, “[a]ccording to the standard theory it is the fact of unlawfulness itself that determines the invalidity of the relevant administrative act: such a decision is “invalid simply by virtue of its unlawfulness””.

It is submitted that the above analysis of the law of habeas corpus throws this theory into doubt, at least in relation to non-jurisdictional errors made within imprisonment decisions. Imagine for a moment a prisoner, P, whose detention authorisation had been vitiated by some public law error, such as a non-jurisdictional error of law. If the treatment of P was unlawful from the moment the authorisation decision was promulgated, what would prevent her from bringing an action (against her ‘gaoler’) challenging directly the lawfulness of his detention? What would prevent a court from asking the simple question (the one that Sir William Wade argued should be asked in habeas corpus actions in “Habeas Corpus and Judicial Review” (1997) 113 LQR 55 at 62) “is this detention unlawful?” in a habeas corpus action? Instead, the authoritative position from Cheblak states that the authorisation decision would constitute a complete answer to the writ, rendering it (at least temporarily) unavailable. Only once that decision is set aside does the imprisonment become prospectively unlawful. The writ of habeas corpus would issue if the imprisonment continued after that decision was set aside; there is no unlawfulness of the imprisonment until that point. The fact that an as-of-right action for habeas corpus is precluded until the underlying administrative authorisation is set aside implies that the detention’s unlawfulness only obtains after the decision is set-aside in judicial review proceedings.

One might rejoin that this formulation is too simplistic: it conflates the issue of whether an administrative act is a nullity with the consequences of the finding of a nullity. It is perfectly possible that, at the moment that P’s authorisation decision is set aside, it is treated in law as having been void ab initio from that point onwards, and legal consequences could retroactively flow from this finding. But the structure of the law as above formulated appears to run against this criticism. The writ of habeas corpus issues as a matter of right. If the authorisation decision was challenged on the basis of a jurisdictional error, the Lord Donaldson MR formulation means that the prisoner could challenge their detention from the time it was authorised as a matter of right, implying that the detention was unlawful from the beginning. But where a non-jurisdictional error is alleged, one has to bring judicial review and then later a habeas corpus action, implying that the detention was only unlawful from the time that the authorisation was set aside under judicial review. The automatic right of habeas corpus only issues when the impugned decision makes a jurisdictional error.

The Supreme Court decision in the Continuity case

This brings us onto the Supreme Court decision in the Continuity case. In this case, the Court ruled that an element of the Scottish Parliament’s UK Withdrawal from the European Union (Legal Continuity) (Scotland) Bill fell beyond Holyrood’s legislative competence. At para. 26, the Court stated that:

“There is a difference between a want of legislative competence and more general grounds for judicial review on public law grounds.  The  result  of  a  want  of  legislative  competence  is  that  a  Scottish enactment is a nullity (“not law”): see section 29(1) of the Scotland Act. A Scottish enactment which is held by a court to be unlawful on more general public law grounds is not necessarily a nullity.”

Plainly, the context of this statement is very different to that of Cheblak. The Supreme Court is addressing competence, not jurisdiction. Moreover, the terminology of “not law” is taken directly from section 29(1) of the Scotland Act 1998. Nonetheless, this judicial statement does appear to run neatly alongside some of the comments I have made thus far. Where an administrative act falls outside the competence or jurisdiction of the decision-maker, that act can be treated as not law from its inception. It can be challenged as such, and any real-world consequences flowing from that administrative act (such as imprisonment) can be challenged as a matter of course, as through the writ of habeas corpus. But where an administrative act is defective through its making of some public law error, only the discretionary remedy of judicial review will be available. It remains to be seen whether such a distinction, which problematises the more unitary way the “nullity” debate has been framed thus far, will take hold in other areas of law.


The famous case of Anisminic Ltd v Foreign Compensation Commission  is credited with making the foundational breakthrough in UK public law that, whenever an administrative decision-maker makes an error of law, such renders the decision outwith their jurisdiction, and renders that decision a “nullity”. What Anisminic did not elaborate upon was the nature of this “nullity”. It appears that, in at least the two areas of law discussed above, the quality of the nullity assigned to an administrative act is contingent on the type of error made. Where the error goes to jurisdiction (or competence), it appears that that act is automatically void. Where the error is non-jurisdictional, then that act is void in some less absolute sense. That is, the consequences of a finding of nullity in a non-jurisdictional case are a matter of discretion, whereas voidness follows from a finding of jurisdictional error as a matter of course. An alternative reading is that only some legal errors render a decision a (true) nullity, while others instead grant the court a discretion as to the remedial consequences of its findings.

Finnian Clarke is a BPTC student and Tutor in EU Law at the London School of Economics.

(Suggested citation: F. Clarke, ‘Habeas Corpus and the Nature of “Nullity” in UK Public Law’, U.K. Const. L. Blog (8th Oct. 2019) (available at