[The IPKat] Recent consideration of estoppel doctrines in Australian patent proceedings confirms the bar remains high
Claire Gregg
Recent consideration of estoppel doctrines in Australian patent proceedings confirms the bar remains high
Dr Claire Gregg Monday, June 29, 2026 - #patents, abuse of process, Anshun estoppel, Australia, Claire Gregg, issue estoppel, OzKat
The recent Federal Court of Australia decision in Orikan Pty Ltd v Vehicle Monitoring Systems Pty Limited (No 2) [2026] FCA 407 (Orikan No. 2) provides a timely reminder that, in Australian patent litigation, the bar for successful estoppel arguments is high. In particular, the decision considered issue estoppel and Anshun estoppel, as well as abuse of process, in circumstances where unsuccessful grounds of opposition and earlier claim construction findings were allegedly re-litigated by the parties in later infringement and revocation proceedings.
Estoppel doctrines in Australia
While the doctrines of issue estoppel and Anshun estoppel are well-established features of the Australian legal landscape, their consideration in patent disputes is relatively rare and they are even more rarely applied.
Issue estoppel
Issue estoppel precludes re-litigation of issues of fact or law necessarily determined in earlier proceedings between the same parties (or their privies). Essentially, issue estoppel arises where the same question has already been decided in earlier court proceedings, the earlier decision is final, and the parties or their privies (e.g., predecessors in title) are identical. This doctrine is informed by considerations of finality and fairness, and extends only to matters that were legally indispensable to the earlier determination.
Anshun estoppel
Anshun estoppel (first articulated in Port of Melbourne Authority v Anshun Pty Ltd [1981] HCA 45) applies where a party fails to raise in earlier proceedings a claim or issue so closely connected with the subject matter that it was unreasonable not to have raised it then. This doctrine is informed by considerations of finality, reasonableness, and the avoidance of inconsistent judgments. Like issue estoppel, Anshun estoppel applies only between the parties or their privies.
Abuse of process
While not itself a form of estoppel, abuse of process was also raised in Orikan No. 2 alongside Anshun estoppel. Abuse of process arises where "the use of a court's procedures would be unjustifiably oppressive to a party or would bring the administration of justice into disrepute" (Tomlinson v Ramsey Food Processing Pty Limited [2015] HCA 28). This doctrine is informed by considerations such as the just determination of proceedings, efficient use of judicial and administrative resources, the efficient disposal of the Court's overall caseload, timely resolution of disputes, and resolution of disputes at reasonable cost.
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Background to Orikan No. 2 proceedings
Orikan No. 2 concerned Australian Patent No. 2013213708 (Patent) owned by Orikan Pty Ltd (Orikan), the assignee of related entity SARB Management Pty Ltd (SARB). The Patent broadly claimed.
1. A vehicle detection unit (VDU) comprising:
a magnetic sensor able to sense variations in magnetic field and for outputting a sensor signal caused by occupancy of a vehicle space by a vehicle;
a storage device carrying parameters which define notifiable vehicle space occupancy events;
a processor operable to process the sensor signal to determine occupancy status of the vehicle space, and operable to compare the occupancy status of the vehicle space with the parameters in order to determine whether a notifiable event has occurred, and operable to initiate a communication from the vehicle detection unit to a supervisory device upon occurrence of a notifiable event, wherein the communication includes data items pertaining to the notifiable event and communicated in a format suitable for pre population into infringement issuing software.
Vehicle Monitoring Systems Pty Limited (VMS) unsuccessfully opposed grant of the Patent before the Patent Office, including on the basis that the claims lacked sufficiency (Vehicle Monitoring Systems Pty Ltd v SARB Management Group Pty Ltd [2017] APO 63). VMS also unsuccessfully appealed the Patent Office decision to the Federal Court (Orikan Pty Ltd v Vehicle Monitoring Systems Pty Limited [2020] FCA 408). A further appeal to the Full Federal Court was also dismissed (Vehicle Monitoring Systems Pty Ltd v SARB Management Group Pty Ltd [2021] FCAFC 224), which decision was final (Final Opposition Judgment).
In the Final Opposition Judgment, the Full Court also made claim construction findings that were important to its finding that the claims involve an inventive step.
Estoppel issues in Orikan No. 2
Orikan sued VMS for infringement of the Patent by the exploitation of its vehicle parking overstay detection systems using the in-ground vehicle detection sensor unit known as a PODS Sensor. VMS cross-claimed for revocation of the Patent, including on the basis of insufficiency. VMS argued that Orikan was barred by issue estoppel from advancing a different construction from that adopted in the Final Opposition Judgment. Orikan, in turn, argued that VMS was barred by issue estoppel, Anshun estoppel, or abuse of process from advancing aspects of its insufficiency case said to have been resolved, or that should have been raised, in the Final Opposition Judgment.
Issue estoppel
The Court considered that the construction findings in the Final Opposition Judgment were legally indispensable to the dismissal of the opposition appeal, and that SARB (of which Orikan was a privy) had obtained the benefit of those construction findings in defeating VMS's inventive step challenge. Accordingly, considerations of finality and fairness required that Orikan accept the burden of that construction in the later infringement proceeding.
In relation to sufficiency, the Court focused on whether the same issue had been determined in the Final Opposition Judgment. In that case, the sufficiency challenge concerned whether the specification disclosed that the VDU should be selected to perform formatting tasks. By contrast, the later challenge concerned whether the specification sufficiently disclosed the processing of sensor signals to determine occupancy status and notifiable events. As these were distinct factual issues, no issue estoppel arose in relation to sufficiency.
Anshun estoppel
In an earlier interlocutory proceeding between the parties in Orikan Pty Ltd v Vehicle Monitoring Systems Pty Limited [2023] FCA 1031 (Orikan No. 1), Orikan sought to estop VMS from bringing the invalidity cross-claim on the basis of Anshun estoppel and abuse of process. The interlocutory application was dismissed on the basis that, although VMS could have raised the invalidity grounds in the earlier opposition proceedings:
· the Court was not satisfied there was a risk of inconsistent judgments, and it was likely that different facts and issues would arise;
· there is a fundamental difference in the nature and consequences of opposition (pre-grant) and infringement/revocation proceedings (invalidity cross-claim raised as defence to infringement);
· VMS would suffer significant prejudice if it were not allowed to defend against Orikan's infringement allegation by counter-claiming for invalidity; and
· the Court was not satisfied that additional cost and delay would be incurred as a result of VMS's invalidity cross-claim.
The Court also noted that its conclusion might have been different if VMS had initiated the proceedings against Orikan.
At trial in Orikan No. 2, the Court substantially echoed the reasoning in Orikan No. 1 in finding that neither Anshun estoppel nor abuse of process arose.
Abuse of process
The Court in Orikan No. 1 did not consider that Orikan would suffer unjustifiable oppression if the invalidity cross-claim were allowed to proceed. In that regard, the Court considered that Orikan should reasonably have expected an invalidity cross-claim when it commenced infringement proceedings against VMS. Nor did the Court consider that VMS's invalidity cross-claim would bring the administration of justice into disrepute. The reasoning was closely aligned with its analysis of Anshun estoppel. In Orikan, the Court again echoed the reasoning in Orikan No. 1.
Final thoughts
While estoppel doctrines are available in Australia, the courts exercise a high degree of caution in applying them in patent cases to balance finality against the public interest in ensuring invalid patents can be revoked. Comparisons may be drawn with the UK doctrines of issue estoppel and the Henderson v Henderson principle (which is similar to Anshun estoppel and abuse of process), although the Australian courts may be less ready than UK courts to invoke abuse of process in patent proceedings. Like the UK and European courts, Australia also recognises cause of action estoppel (or res judicata).
The key takeaway from Orikan No. 2 is not merely that estoppel arguments in Australian patent litigation face a high bar to success, but also that success will likely depend on demonstrating a close connection between the precise issues previously determined and those sought to be re-agitated. Where such a connection cannot be established, Orikan No. 2 makes clear that the courts are unlikely to estop a party from advancing a factually distinct case of invalidity (even if the same general ground of invalidity has previously been determined). Orikan No. 2 also highlights that where a party has derived a benefit from a particular claim construction in earlier proceedings, they are likely to be estopped from advancing an alternative construction in later proceedings.
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