An Analysis of Aguasa v Hunter [2026] WASCA 37
1. Introduction
Aguasa v Hunter [2026] WASCA 37 is the first appellate decision in Western Australia to determine whether the mandatory concerns notice requirement under s 12B of the Defamation Act 2005 (NSW) is a substantive law for the purposes of the choice of law provision in s 11(1) of the Defamation Act 2005 (WA). The Court of Appeal (Mitchell JA, Vaughan JA, and Cobby J) unanimously held that s 12B is substantive in character, with the consequence that a plaintiff commencing defamation proceedings in Western Australia in respect of matter published wholly in New South Wales must comply with the NSW concerns notice regime before filing proceedings.
The decision is of considerable practical significance for WA defamation practitioners. Western Australia has not adopted the 2021 uniform defamation reforms enacted in New South Wales, Queensland, Victoria, South Australia, Tasmania, and the Australian Capital Territory (at [17]). Those reforms introduced, among other things, a “serious harm” element to the cause of action (s 10A), a mandatory concerns notice regime (ss 12A–12B), a public interest defence (s 29A), and the removal of the triviality defence (at [16]–[17], [84]). Until Aguasa, it was arguable—supported by the obiter reasoning of Applegarth J in Peros v Nationwide News Pty Ltd [2024] QSC 80—that a WA plaintiff could avoid the concerns notice requirement by commencing proceedings in Western Australia, treating s 12B as merely procedural and therefore not picked up by s 11(1) of the WA Act.
That argument has now been decisively rejected. The decision requires WA practitioners to identify, at the outset of any defamation retainer, the jurisdiction in which the relevant publication occurred, to ascertain whether that jurisdiction has enacted a mandatory concerns notice regime, and to comply with the requirements of that regime before issuing proceedings. Failure to do so may result in the summary dismissal of the proceedings, as occurred at first instance before Tottle J (Aguasa v Hunter [2024] WASC 380) and as was upheld on appeal.
2. Relevant Legal Framework
The choice of law provision: s 11(1) of the WA Act
Section 11(1) of the Defamation Act 2005 (WA) provides that if a matter is published wholly within a particular Australian jurisdictional area, the substantive law applicable in that area must be applied in Western Australia to determine any cause of action for defamation based on the publication. The term “Australian jurisdictional area” includes each State and Territory: s 11(5)(a).
The provision gives effect to a “no advantage” principle. As Vaughan JA explained, s 11(1) evinces a legislative choice that it is undesirable for a plaintiff to receive a substantive advantage by suing in one forum rather than another (at [92]–[93]). Importantly, the substantive law of the other jurisdiction is applied in WA by operation of the WA Act itself; the law does not operate extraterritorially as a law of the other jurisdiction (at [90]–[91]).
The distinction between substantive and procedural law
The distinction between substantive law and procedural law is fundamental to this decision and warrants brief explanation. Substantive law is concerned with the rights, duties, and obligations of parties. It determines what a party is entitled to, what defences are available, and what remedies may be granted. Procedural law, by contrast, governs the manner in which those rights and duties are enforced—the machinery of litigation. It prescribes the steps by which a party brings and conducts court proceedings, such as rules about filing, service, pleading, and evidence.
The distinction matters in a choice of law context because, when a court in one jurisdiction applies the law of another, it ordinarily applies only the substantive law of the other jurisdiction and follows its own procedural rules. A WA court hearing a defamation claim governed by NSW substantive law will apply the NSW rules about the elements of the cause of action, available defences, and quantification of damages, but will follow WA procedural rules about how the proceedings are conducted.
In practice, the line between substance and procedure is not always clear. A legislative requirement that a plaintiff take a step before commencing proceedings—such as giving a notice—sits at the boundary. If such a requirement is characterised as procedural, it forms part of the machinery of the forum court and need not be complied with where proceedings are commenced in a different jurisdiction. If it is characterised as substantive, it attaches to the cause of action itself and must be complied with wherever the proceedings are commenced. That is the central question addressed in Aguasa v Hunter.
The uniform defamation law framework
The WA and NSW Acts were enacted in 2005 as part of uniform model provisions agreed to by all State and Territory Attorneys General. They were in substantially identical terms until the NSW Act was amended by the Defamation Amendment Act 2020 (NSW), effective 1 July 2021 (at [15]–[16], [82]–[83]).
The 2020 NSW amendments
The amendments introduced several significant changes, including the serious harm element (s 10A), the mandatory concerns notice regime (ss 12A–12B), a reformed s 18 defence, an extension of the limitation period to accommodate the concerns notice process (Limitation Act 1969 (NSW), s 14B(2)–(3)), and a new public interest defence (s 29A) (at [16], [84]).
The substantive/procedural distinction
The foundational authority is John Pfeiffer Pty Ltd v Rogerson [2000] HCA 36; (2000) 203 CLR 503. The plurality identified two guiding principles: first, matters that affect the existence, extent, or enforceability of rights or duties are matters of substance; and second, rules directed to governing or regulating the mode or conduct of court proceedings are procedural (at [99]). As Vaughan JA observed, these are not alternative formulations but complementary descriptions of the same conceptual distinction (at [162]–[164]).
The key “notice before action” authority is Hamilton v Merck and Co Inc [2006] NSWCA 55, in which the NSW Court of Appeal characterised pre-commencement requirements under the Personal Injuries Proceedings Act 2002 (Qld) as procedural. Spigelman CJ recognised, however, that such a prohibition on commencement of proceedings is “capable” of constituting a substantive condition precedent where employed in a legislative scheme that creates a new right or substitutes a legislative scheme for pre-existing common law rights (at [34], [171]–[172]).
In Wickham Freight Lines Pty Ltd v Ferguson [2013] NSWCA 66, the NSW Court of Appeal held that provisions which were integral parts of a legislative package limiting common law entitlements could not be isolated as procedural, even where they regulated the process by which the entitlement was established (at [37], [175]–[177]).
Peros v Nationwide News Pty Ltd [2024] QSC 80 was the only prior decision to directly address s 12B in the defamation context. Applegarth J held, in obiter, that s 12B of the Queensland equivalent was procedural, reasoning that it regulated the enforcement of a pre-existing common law right and was analogous to the provisions considered in Hamilton (at [50]–[58], [180]–[185]).
3. The Facts of the Case
The appellant, Ms Aguasa, commenced defamation proceedings against the respondents, Ms Hunter and Ms Cotter, in the Supreme Court of Western Australia on 29 November 2023 (at [74]). The proceedings concerned emails published by the respondents on 18 August 2023 to a third party located in New South Wales (at [1], [74]). It was an agreed fact that publication occurred wholly within New South Wales (at [1]).
It was also agreed that the appellant gave no notice—whether a concerns notice within the meaning of the NSW Act or otherwise—to either respondent prior to serving the writ of summons (at [75]).
The respondents applied to Tottle J, as case manager, to dismiss the proceedings on the ground that the appellant had failed to comply with s 12B(1) of the NSW Act (at [3], [76]–[77]). The appellant accepted that, by operation of s 11(1) of the WA Act, the substantive law of NSW applied, but contended that s 12B was procedural and therefore not picked up by s 11(1) (at [78]).
The primary judge held, with “some hesitation,” that s 12B was substantive and dismissed the proceedings (at [4], [79]–[80]).
4. Analysis of the Court’s Reasoning
The joint reasons: Mitchell JA and Cobby J
Mitchell JA and Cobby J approached the characterisation by considering the 2020 NSW amendments as a coherent legislative package. Their Honours identified four reasons why s 12B should be characterised as substantive.
First, the enactment of s 10A introduced a new element of the cause of action (serious harm), representing a substantive change to the existing law (at [41]).
Second, ss 12A and 12B restrict the right to commence proceedings for defamation. The court lacks power to excuse non-compliance with s 12B(1)(a) (the concerns notice requirement) or to permit reliance on imputations not identified in the concerns notice under s 12B(1)(b). Each of those provisions therefore concerns the “existence, extent and enforceability” of the aggrieved person’s right to commence proceedings (at [42]–[45]).
Third, the amendments to the Limitation Act 1969 (NSW) extending the limitation period to accommodate the concerns notice process are ordinarily to be characterised as substantive, consistent with John Pfeiffer (at [46]).
Fourth, the availability of the s 18 defence is conditioned upon the issue of a concerns notice. A construction of s 12B that renders the s 18 defence unavailable because no concerns notice was issued is to be avoided (at [48]–[49], [63]).
The separate reasons: Vaughan JA
Vaughan JA arrived at the same conclusion but by a different analytical route, providing separate reasons that addressed additional arguments raised by the appellant. His Honour accepted several propositions that were, in isolation, favourable to the appellant.
Vaughan JA accepted that pt 3 of the NSW Act, viewed holistically, is “distinctly more procedural than substantive” (at [203]). His Honour also accepted that, standing alone, s 12B(1)(a) does not modify or extinguish the general law right to damages for defamation; it is concerned only with the procedural means by which the cause of action is commenced (at [228]). Further, Vaughan JA accepted that the statutory purpose behind the concerns notice regime is to avoid litigation altogether, which is “distinctly procedural in nature” (at [215]–[216]).
Despite these concessions, Vaughan JA held that the determinative factor was the interaction between s 12B(1)(a) and the defence of failure to accept a reasonable offer to make amends in s 18(1) of the NSW Act. The s 18(1) defence is substantive—it provides a defence to an action, thereby precluding a remedy and affecting the enforceability of rights (at [244]). The defence is predicated on the giving of a concerns notice under s 12A (at [129], [242]). Accordingly, if s 12B(1)(a) is characterised as procedural, the s 18(1) defence becomes unavailable in proceedings commenced in WA—a result contrary to the “no advantage” principle evinced by s 11(1) of the WA Act (at [241]).
In Vaughan JA’s analysis, s 12B(1)(a) is “inseparable from and ought not be considered in isolation as fulfilling a function distinct from the substantive defence provided for in s 18(1)” (at [251]). The concerns notice regime has a “continuing consequence” for the purpose of the substantive defence; it is “an integral part of a legislative package that has as one of its key features a substantive defence in s 18(1)” (at [249]).
Departure from Peros
All members of the Court respectfully declined to follow Applegarth J’s obiter reasoning in Peros. Mitchell JA and Cobby J considered that Applegarth J’s analysis of the s 18 defence—which characterised the unavailability of the defence as merely a consequence of s 12B “simply not applying” in a rare case—was unsatisfactory (at [59]–[63]). Vaughan JA considered that Applegarth J’s reasoning on this point was grounded in the anterior extraterritoriality finding, which did not arise in the present appeal (at [254]).
5. Assessing the Consequences
Immediate procedural consequences
The immediate consequence of the decision is that defamation proceedings commenced in WA without a concerns notice compliant with the law of the place of publication will be liable to summary dismissal. This follows from the NSW Court of Appeal’s holding in Cavar v Campbelltown Catholic Club Ltd [2024] NSWCA 126 that it is “clearly correct” to summarily dismiss proceedings commenced in contravention of s 12B(1) (at [76]).
The s 18 defence
A critical practical consequence is that the s 18 defence under the NSW Act—predicated on a concerns notice having been issued—replaces the s 18 defence under the WA Act in proceedings to which s 11(1) applies. The WA Act’s s 18 defence, which requires only that the publisher made an offer “as soon as practicable after becoming aware” that the matter is or may be defamatory, will not be available. The NSW Act’s s 18 defence requires both the receipt of a concerns notice and the making of an offer within the applicable period (at [25]–[26], [127]–[129]).
Limitation period implications
Where s 11(1) of the WA Act applies to pick up NSW substantive law, the limitation provisions of the Limitation Act 1969 (NSW) will also apply by operation of s 5 of the Choice of Law (Limitation Periods) Act 1994 (WA) (at [89], [119]). This includes s 14B(2)–(3) of the Limitation Act 1969 (NSW), which extends the one-year limitation period by up to 56 days where a concerns notice is given within 56 days of the limitation period’s expiry (at [22]–[23], [117]–[118]).
Broader implications for non-reform jurisdictions
Western Australia and the Northern Territory are the only Australian jurisdictions that have not adopted the 2021 uniform defamation reforms (at [17]). The decision means that WA’s non-adoption of the reforms offers no practical advantage to a plaintiff in respect of publications occurring in reform jurisdictions. The “no advantage” principle embedded in s 11(1) of the WA Act ensures that the substantive law of the place of publication governs, regardless of the forum chosen.
6. Worked Example
Hypothetical: A Perth-based business owner discovers that a former employee has published a defamatory post on social media on 1 February 2026. The post is accessible to and read by recipients in Queensland, where the former employee resides. There is no evidence of publication outside Queensland. The business owner consults a WA lawyer on 15 March 2026.
Identification of applicable law
Publication occurred wholly within Queensland. By operation of s 11(1) of the WA Act, the substantive law of Queensland must be applied. Queensland has adopted the 2021 uniform defamation reforms. The Defamation Act 2005 (Qld) includes an equivalent mandatory concerns notice regime (ss 12A–12B) and the reformed s 18 defence.
Pre-action steps required
The lawyer must prepare and serve a concerns notice complying with s 12A of the Queensland Act. The notice must: (a) be in writing; (b) specify the location where the matter can be accessed (the social media URL); (c) inform the publisher of the defamatory imputations; and (d) inform the publisher of the serious harm to the aggrieved person’s reputation.
Timing
The limitation period is one year from publication: 1 February 2027. If the concerns notice is served by 15 March 2026, the applicable period for an offer to make amends is 28 days (s 14(2)(b)). Proceedings may not be commenced before expiry of that period unless leave is granted under s 12B(3). If the concerns notice is served within 56 days before 1 February 2027 (i.e. after 7 December 2026), the limitation period is automatically extended under the Queensland equivalent of s 14B(2)–(3).
Consequences of non-compliance
If the lawyer issues proceedings in WA without a compliant concerns notice, the defendant may apply for summary dismissal. Based on Aguasa and Cavar, such an application will succeed. The s 18 defence under the WA Act will not be available to the defendant; only the Queensland Act’s s 18 defence (requiring a concerns notice) will apply.
Defendant’s position
If a compliant concerns notice is served, the defendant should consider making an offer to make amends within the applicable period. A reasonable offer, if not accepted, provides the defendant with the substantive defence under s 18(1) of the Queensland Act. Failure to make such an offer within the applicable period forecloses the defence.
7. Practitioner Guidance: A Step-by-Step Framework
Step 1: Identify the place of publication. At the outset of every defamation retainer, determine where the relevant matter was published. If the matter was published wholly within a single Australian jurisdiction, s 11(1) of the WA Act applies and the substantive law of that jurisdiction governs. If the matter was published across multiple jurisdictions, s 11(2) applies and the law of the jurisdiction with the closest connection to the harm governs. In either case, the applicable substantive law must be ascertained before any pre-action steps are taken.
Step 2: Determine whether the applicable jurisdiction has adopted the 2021 reforms. As at the date of this article, all Australian jurisdictions except Western Australia and the Northern Territory have enacted mandatory concerns notice regimes. If the applicable jurisdiction is a reform jurisdiction, s 12B applies as a substantive law: Aguasa at [6], [73], [256].
Step 3: Prepare a compliant concerns notice. Ensure the concerns notice complies with the requirements of s 12A of the applicable jurisdiction’s legislation. This includes the serious harm requirement in s 12A(1)(a)(iv), which does not appear in the WA Act’s definition of a concerns notice (s 14(2) of the WA Act). The concerns notice must identify the imputations to be relied upon in any subsequent proceedings, as the plaintiff will be confined to those imputations or imputations substantially the same: s 12B(1)(b), s 12B(2).
Step 4: Serve the concerns notice and allow the applicable period to elapse. The applicable period for an offer to make amends is ordinarily 28 days (s 14(2)(b)). If the publisher requests further particulars under s 12A(3), the applicable period runs from 14 days after those particulars are provided (s 14(2)(a)). Proceedings cannot be commenced before the applicable period elapses, unless leave is granted under s 12B(3).
Step 5: Consider limitation period implications. If the concerns notice is served within 56 days of the one-year limitation period’s expiry, s 14B(2)–(3) of the Limitation Act 1969 (NSW) (or its equivalent) extends the limitation period automatically. Calculate the applicable dates at the outset to avoid being statute-barred. The limitation provisions apply as part of the substantive law by operation of s 5 of the Choice of Law (Limitation Periods) Act 1994 (WA): Aguasa at [89], [119].
Step 6: For defendants, respond to the concerns notice promptly. A publisher who receives a concerns notice should consider making an offer to make amends within the applicable period. The s 18(1) defence under the NSW Act requires the offer to have been made “as soon as reasonably practicable after the publisher was given a concerns notice” and “within the applicable period” (s 18(1)(a)). Delay may forfeit the defence.
Step 7: Document compliance. Retain evidence of service of the concerns notice and the date on which the applicable period elapses. If the publisher requests further particulars, retain copies of the request and the response. This documentation will be critical if the defendant challenges the validity of the concerns notice or the timing of commencement.
8. Evidence and Arguments Available to Each Side
For the plaintiff (aggrieved person)
• Compliance evidence: Retain copies of the concerns notice, proof of service, and evidence that the applicable period elapsed before proceedings were commenced.
• Imputation particulars: Ensure that all imputations pleaded in the statement of claim were particularised in the concerns notice, or are substantially the same as those particularised: s 12B(1)(b), s 12B(2)(b). Detailed imputation drafting at the concerns notice stage is essential, as the plaintiff will be confined to those imputations or substantially similar ones.
• Serious harm evidence: Prepare evidence of serious harm at the concerns notice stage, as s 12A(1)(a)(iv) requires the notice to inform the publisher of the alleged serious harm. This evidence will also be required at the s 10A stage of proceedings.
• Leave applications: If the limitation period is imminent and the applicable period has not elapsed, consider applying for leave under s 12B(3). The court may grant leave if it is just and reasonable to do so (s 12B(3)(b)) or the proceedings will be statute-barred once the applicable period has expired (s 12B(3)(a)).
For the defendant (publisher)
• Non-compliance challenge: If proceedings are commenced without a compliant concerns notice, apply for summary dismissal. Aguasa and Cavar establish that summary dismissal is the appropriate remedy.
• Concerns notice deficiency: Challenge the adequacy of the concerns notice under s 12A. If the notice fails to adequately particularise the information required by s 12A(1)(a)(ii)–(v), the publisher may issue a further particulars notice under s 12A(3). If the aggrieved person fails to provide reasonable further particulars within 14 days, the aggrieved person is taken not to have given a concerns notice: s 12A(5).
• Section 18 defence: If a concerns notice is received, make an offer to make amends promptly and within the applicable period to preserve the s 18(1) defence. Document the reasonableness of the offer.
• Imputation confinement: If the plaintiff pleads imputations not particularised in the concerns notice and not substantially the same, challenge those imputations as impermissible under s 12B(1)(b) and s 12B(2)(b). The court has no power to excuse non-compliance with s 12B(1)(b): Aguasa at [44].
9. Key Takeaways for Legal Practice
1. Section 12B of the NSW Act is substantive. The WA Court of Appeal has unanimously held that the mandatory concerns notice requirement under s 12B of the NSW Act (and by extension, its equivalents in other reform jurisdictions) is a substantive law for the purposes of s 11(1) of the WA Act. This is now settled law in Western Australia.
2. The concerns notice regime of the place of publication applies. Where a defamatory matter is published wholly within a reform jurisdiction, the concerns notice requirements of that jurisdiction must be complied with before proceedings are commenced in WA. A concerns notice compliant with the WA Act will not suffice if the applicable law is that of NSW, Queensland, or another reform jurisdiction.
3. The interaction with the s 18 defence is determinative. The reasoning of both the joint judgment and Vaughan JA identifies the interaction between s 12B(1)(a) and the s 18(1) defence as a critical, and ultimately determinative, factor. The s 18 defence is substantive; characterising s 12B as procedural would render the s 18 defence unavailable, contrary to the “no advantage” principle.
4. The WA Act’s s 18 defence is displaced. Where s 11(1) of the WA Act applies, the substantive law of the place of publication replaces the substantive law of WA. This means the WA Act’s s 18 defence—which does not require a concerns notice—is not available. It is not a mandatory law of the forum: Aguasa at [65], [151]–[153].
5. Peros is not to be followed. The obiter reasoning of Applegarth J in Peros that s 12B is procedural has been respectfully declined by all three members of the WA Court of Appeal. Practitioners should not rely on Peros as authority for characterising s 12B as procedural.
6. Imputation drafting at the concerns notice stage is critical. The plaintiff is confined to imputations particularised in the concerns notice, or imputations substantially the same (s 12B(1)(b), s 12B(2)). Careful and comprehensive imputation drafting at the pre-action stage is essential. The court has no power to excuse non-compliance: Aguasa at [44].
7. Limitation period calculations must account for the concerns notice process. Practitioners must calculate the applicable period for an offer to make amends (ordinarily 28 days) and any potential extension of the limitation period under the applicable limitation legislation when planning the timing of concerns notices and proceedings.
8. The cross-vesting legislation does not alter the analysis. The Court rejected the argument that s 11(1) of the Jurisdiction of Courts (Cross-vesting) Act 1987 (WA) could affect the characterisation of s 12B or the availability of the WA Act’s s 18 defence (at [66]–[68], [154]–[157]).
9. WA’s non-adoption of the reforms does not insulate WA plaintiffs. The decision underscores that WA’s failure to adopt the 2021 uniform defamation reforms offers no advantage to a plaintiff whose publication occurred in a reform jurisdiction. The “no advantage” principle in s 11(1) ensures parity of substantive law regardless of the forum chosen.
10. Broader implications for the substance/procedure distinction. The decision contributes to the developing jurisprudence on the characterisation of notice before action provisions. Vaughan JA’s detailed analysis of the principles from John Pfeiffer, Hamilton, and Wickham Freight Lines provides a structured framework for determining whether a notice before action requirement is substantive or procedural, with particular emphasis on whether the requirement interacts with other substantive provisions of the legislative regime.
10. Conclusion
Aguasa v Hunter resolves a question of significant practical importance for WA defamation practitioners. The decision establishes that the mandatory concerns notice requirement enacted by reform jurisdictions is a substantive law that applies in WA proceedings by operation of s 11(1) of the WA Act. The characterisation turns not on the procedural appearance of s 12B in isolation, but on its inseparable connection to the substantive defence in s 18(1)—a connection that gives the concerns notice regime a continuing significance well beyond the pre-action phase.
For practitioners, the core message is one of diligence at the intake stage. The jurisdiction of publication must be identified, the applicable concerns notice regime ascertained, and compliance achieved before proceedings are filed. Defendants, equally, must understand that the s 18 defence under the applicable jurisdiction—not the WA Act—governs their position, and must respond to concerns notices promptly and within the statutory timeframe.
The decision also highlights the consequences of WA’s continued divergence from the uniform defamation law framework. While WA retains the pre-reform regime for publications occurring within its borders, the practical reality is that WA practitioners are increasingly required to navigate the reformed regime when acting in respect of interstate publications. A working knowledge of the concerns notice requirements under the NSW Act and its counterparts is now indispensable.