On 13 March 2018, Nauru unilaterally terminated its bilateral treaty (‘Nauru Treaty’) with Australia. This treaty had been implemented by domestic law: the Nauru (High Court Appeals) Act 1976 (Cth) (‘Appeals Act’) granted the High Court jurisdiction to hear appeals from the Supreme Court of Nauru. The termination of the underlying treaty marked the end of an unusual arrangement that has existed between the two countries for just over 40 years. It did not attract much media or political attention. Furthermore, it is assumed that consequent to the termination, the High Court’s jurisdiction to hear appeals from Nauru ‘disappears’.

This post examines the merits behind this assumption. Would a law enacted under the treaty implementation aspect of the external affairs power (s 51(xxix) of the Australian Constitution) retain its validity if the relevant treaty is subsequently terminated? As will become apparent, the peculiar situation created by the termination of the Nauru Treaty highlights a fundamental uncertainty about the operation of the external affairs power. Furthermore, it raises a broader question as to whether a validly enacted law can ‘become’ invalid as the underlying facts on which its validity depends change. This post contends that it is possible, and indeed desirable, to recognise that factual change can lead to invalidation of a once valid statute.

The Nauru Treaty

What would happen if an unhappy litigant in Nauru wished to appeal to the High Court today? Article 6(2) of the Nauru Treaty provides

2. Termination of this Agreement is not to affect –

(a) the hearing and determination of an appeal from the Supreme Court of Nauru instituted in the High Court before the date of the termination …

It may be inferred from art 6(2) that termination of the treaty would affect the institution of High Court appeals after the date of the termination. Recently in Nauru v WET040 [2018] HCA 56 (7 November 2018), the Court held that a notice of appeal filed out of time prior to the treaty’s termination is effective in “instituting” the appeal within the meaning of art 6(2), even when the extension of time was granted some seven months after termination. The Court accordingly decided that it has jurisdiction to hear the appeal: at [17]. One may regard this as an example of the Court’s implicit acceptance of the fact that it lacked jurisdiction to hear appeals instituted after the treaty’s termination. Indeed, if the Court is satisfied that termination of the treaty would not affect its jurisdiction, there would be no need to decide whether an appeal is “instituted” before the date of the termination.

However, at the time of this post, the legislation implementing the Nauru Treaty — the Appeals Act – remains on Australia’s statute book. Notwithstanding art 6(2), the legal effect of the termination on the operation and validity of the Appeals Act remain unclear. Section 5(1) of the Appeals Act provides that

Appeals lie to the High Court … in cases where the [Nauru Treaty] provides that such appeals are to lie.

Importantly, the grant of jurisdiction under s 5 does not require the Nauru Treaty to remain in force. As a matter of technicality, it may be arguable that Australian domestic law still provides for appeals to the High Court from Nauru in circumstances as provided by the Nauru Treaty. However, political and diplomatic considerations aside, it is absurd for the Appeals Act to remain capable of providing a jurisdictional basis for the High Court to hear fresh appeals from Nauru, in the absence of a treaty in force.

This is by no mean an isolated circumstance. On 6 March 2018, Australia signed a new Maritime Boundary Treaty with Timor-Leste. Upon entry into force of this new treaty, the Timor Sea Treaty concluded in 2002 will be terminated (see art 9(1)). There was no equivalent to Art 6(2). Once that occurs, the constitutional foundation for the Petroleum (Timor Sea Treaty) Act 2003 (Cth) will disappear. Any purported prosecution under ss 6-7 of that Act would therefore run into a similar difficulty.

How can one address this difficulty? A delay between termination of a treaty and repeal of the implementation legislation is inevitable: it would be impractical to expect Parliament to continuously review Australia’s treaty obligations and act instantaneously when a treaty is terminated.

Would termination of a treaty invalidate the implementing statute?

A more reasonable approach is to accept that the termination of the Nauru Treaty automatically renders the Appeals Act constitutionally invalid. The intricacies of the appeal arrangement were explored in this post and elsewhere and need not be repeated here. Relevant to the present discussion, it is sufficient to note that, first, as Stephen Murray explained in his blog, the Appeals Act was drafted on the assumption that it was supported by the external affairs power. Second, the High Court has, by majority, upheld the constitutional validity of the Appeals Act in Ruhani v Director of Police (2005) 222 CLR 489. While the case predominantly concerned a Ch III challenge, it was at least implicitly affirmed that the external affairs power did support the Act (see McHugh J at [33], Gummow and Hayne JJ at [103], Kirby J at [201]).

The external affairs power (or at least its treaty implementation aspect) is a purposive power. A statute falls within the scope of this power if its purpose is to give effect to a treaty. If there is no relevant treaty, then this aspect of the external affairs power is not enlivened: the existence of a treaty is a constitutional fact upon which the validity of a law depends. It was recognised in the Daintree Rainforest Case (1989) 167 CLR 232 that:

When the constitutional support for an impugned law depends upon some matter of fact, a court must decide, in determining the law’s validity, whether the fact exists (at 239).

By corollary, if the requisite fact does not exist, the treaty implementation limb of the external affairs power is not enlivened. If the Nauru Treaty had never existed, the Commonwealth Parliament would lack this source of legislative power to enact the Appeals Act.

One may reason that, since the Act’s validity depended on the fact that it gave effect to the Nauru Treaty, the termination of the treaty is sufficient to render the Act invalid. This would preclude any fresh appeals from being instituted from the moment of termination.

On its face, the proposition that validity of an implementation law depends on the continuous existence of the treaty may not seem controversial. But a logical extension of that proposition is that the validity of a law may change solely due to a change of factual circumstances. This wider proposition has proven to be far more provocative.

The difficulty

A similar line of argument was advanced in Murphy v Electoral Commissioner (2016) 261 CLR 28. Relevantly, the plaintiff argued that because of a change of technology allowing the Australian Electoral Commission to process voter registration almost instantly (i.e. a change of fact), the seven-day ‘suspension period’ between the closing of electoral rolls and polling day has become incompatible with the constitutionally prescribed form of representative government. Counsel for the plaintiff, Brendan Lim, submitted that:

There is nothing incongruous … nor unusually unstable, about validity changing over time where validity depends not only on subject matter characterisation but also on conformity with a purpose or support by a reason.

The Court, however, unanimously dismissed the case. Among the justices who engaged with this submission, French CJ and Bell J held that such an argument ‘would allow a court to pull the constitutional rug from under a valid legislative scheme upon the court’s judgment of the feasibility of alternative arrangements’ (at [42]). More explicitly, Keane J observed that:

the dearth of authority supporting the plaintiffs’ contention that a law valid when made may become invalid by changes in the milieu in which it operates suggests that the plaintiffs’ argument is unorthodox at a fundamental level (at [196]).

Indeed, on its face, the idea that a valid law can ‘become’ invalid is inconsistent with the orthodox understanding of how constitutional invalidity operates in Australia. In a frequently-quoted passage, Latham CJ said in the First Uniform Tax Case (1942) 65 CLR 373:

A pretended law made in excess of power is not and never has been a law at all. Anybody in the country is entitled to disregard it. Naturally he will feel safer if he has a decision of a court in his favour – but such a decision is not an element which produces invalidity in any law. The law is not valid until a court pronounces against it – and thereafter invalid. If it is beyond power it is invalid ab initio (at 408).

In Residual Assco Group Ltd v Spalvins (2000) 202 CLR 629, Kirby J observed that:

The accepted doctrine in this country is that where a statute is found to be constitutionally invalid, such invalidity operates from the moment that the statute in question purportedly came into force. It is thus invalid ab initio (at [58]).

Invalidity arises when a statute is ‘made in excess of power’. It necessarily requires the Court to undertake a close examination of the legal and factual circumstances surrounding the making of a law at the time the law was made. A determination that the law was ‘made’ in excess of power means the law must be invalid from the moment of its inception, i.e., void ab initio.

The void ab initio doctrine seems to reject the notion that factual changes can cause a once valid law to become invalid. At the very least, it overlooks the possibility that those critical facts can change. Why would such an approach be favoured? Perhaps, as hinted by French CJ and Bell J in Murphy, the Court is wary of assuming the somewhat political role of a continuous constitutional watchdog, ready to step in at the instance when a transient change of fact may affect a law’s validity. The policy reason in favouring void ab initio is echoed in Callinan and Heydon JJ’s rejection of the ‘international concerns’ limb of the external affairs power in XYZ v Commonwealth (2006) 227 CLR 532:

… These statements reflect the possibility that at different times a matter may not be of international concern, may then become of international concern, and may then cease to be of international concern again. But if validity is to depend on the position not only at the time of enactment but also at the time of contravention, the outcome will be that the legislation … which was valid when enacted can become invalid. This volatility, and the elusiveness connected with attempts to define “international concern”, strongly suggest that the international concern doctrine do not exist; for if it did, it would operate antithetically to the rule of law (at [218]).

The orthodoxy of void ab initio and the comments in Murphy and XYZ seem to lead to the reasoning that, if a statute can only be invalid ab initio, there will be no room for a change of fact after enactment to have any bearing on the statute’s validity. Applying this line of reasoning to the above thought experiment, given the Court has already found the Appeals Act valid in Ruhani, it must remain valid regardless of the termination of the treaty.

A defence power analogy

The orthodoxy of the void ab initio doctrine is challenged by the High Court’s WWII jurisprudence concerning the defence power. The defence power ‘waxes and wanes’ according to the objective state of war. Certain regulations, such as those prescribing minimum wages for female workers, were found valid during and immediately after the war. However, the Court subsequently found them invalid when they could no longer be justified under the defence power.

Dixon J succinctly summarised the position in Australian Textiles Pty Ltd v Commonwealth (1945) 71 CLR 161: ‘If a power applies to authorise measures only to meet facts, the measure cannot outlast the facts as an operative law’ (at 181). There was no mention of void ab initio, nor was the Court troubled by the notion that such an approach was ‘unorthodox at a fundamental level’.

Just like the treaty implementation aspect of the external affairs power, the defence power is a purposive power, whose scope changes as the underlying purpose changes. An underlying purpose must be determined with reference to and in the context of factual circumstances. The defence power may no longer sustain the same legislation when the fact changes. By parity of reasoning, there is no reason why the same cannot apply to the external affairs power underpinning the Appeals Act. If that is the case, then the Appeals Act would have lost its validity upon the termination of the Nauru Treaty.

Moving beyond the purposive powers?

The significance of an Australian Textiles approach is elevated by the fact that it has not been confined to the defence/purposive power context. The Court has on occasion applied Australian Textiles when examining whether a law contravenes a constitutional limitation. In Armstrong v Victoria [No 2] (1957) 99 CLR 28, Dixon CJ (at 49) and Williams J (at 73-4) acknowledged that change of facts can render an initially valid law invalid for infringing the freedom of interstate trade and commerce provided under s 92 of the Constitution. Williams J explicitly rejected a void ab initio argument. The reformulation of s 92 in Cole v Whitfield is unlikely to affect these reasoning.

With the growing influence of proportionality analysis as applicable to constitutional limitations, there is ample space to apply the Australian Textiles line of reasoning. Under a proportionality analysis, the Court examines whether a piece of legislation is ‘reasonably appropriate and adapted’, or ‘suitable, necessary, and adequate in its balance’ in achieving a legitimate purpose. Regardless of the precise formulation of that analysis, it necessarily entails an exercise of applying the impugned law to a factual state of affairs that may have changed from the time of that law’s enactment. For example, a law that initially conformed with the implied freedom of political communication may no longer satisfy the modified Lange test with the development of technology or social media. Void ab initio can no longer be a satisfactory doctrine in these circumstances. Since all Commonwealth statutes are equally subject to constitutional limitations regardless of their supporting heads of power, Australian Textiles may prove to be more practical.


On the basis of the analogy between the defence power and external affairs power, there are good reasons to argue that the Appeals Act is invalid today. Given the factual circumstances that originally supported the Act’s validity (i.e. the Nauru Treaty being in force) no longer exist, the Act itself may no longer be valid, and hence a disgruntled litigant in Nauru is unlikely to succeed in invoking the High Court’s jurisdiction.

This has broader ramifications for our understanding of the Constitution and the operation of the heads of legislative power. There is an underlying tension between the idea that statutes which lack connection to a head of power are void ab initio – a doctrine regarded as ‘settled’ and ‘accepted’ – and the reasoning employed in a line of cases concerning the defence power – which recognise that a once valid law may become invalid if the underlying facts change. Notwithstanding the High Court’s concern to avoid volatility in the law, it is unsatisfactory to insist that a law once found valid can only remain valid, notwithstanding the ‘changes in the milieu in which it operates’. An Australian Textile approach, recognising that factual change can lead to invalidation of a once valid statute, is more suited to an age of rapid social change.


Ben Ye is an Associate to the Hon Chief Justice Helen Murrell of the ACT Supreme Court.

Suggested citation:  Ben Ye, ‘Can once valid legislation ‘become’ invalid? A case study of the High Court’s (now-lost) Nauru jurisdiction’ on AUSPUBLAW (28 November 2018) <>.