Willem practices primarily in commercial, public law & regulatory matters.

Practice

In commercial law, Willem advises and appears in a range of matters involving contracts, property, torts, professional negligence,, equity (including wills & estates), and building and construction.

In public law he advises and appears in administrative  law matters involving questions of statutory interpretation, merits and judicial review, and in particular proceedings with a focus on disciplinary review, regulatory, environmental & planning law.

He accepts briefs from prosecuting authorities, government bodies and agencies and acts for a range of different clients, including insurers, corporations and individuals. As well as regular advice and appearance work he is briefed for Inquiries, examinations, interlocutory applications, and, complex procedural questions of law and evidence.

Background

Willem is a founding member of Ah Ket Chambers, 500 Bourke Street. Immediately before coming to the Bar he was a Judicial Associate and also practised as a solicitor for several years. Previously, Willem has worked for an international company based in The Netherlands and also completed an extended internship in the area of climate change and desertification.

Willem graduated with a Juris Doctor from Melbourne University. He has completed studies in Dutch law and holds a Masters of European and Public International Law (Hons) alongside a degree in Town Planning.  .

Recent cases

Some matters in which Willem has advised or appeared include:

Commercial

• Manos v House & Pandey [2026] SCVCA (Appeal, Registration of Foreign Judgment, ongoing);
• Stewart-Mole & Anor v Leem Lawyers [2026] SCV (Costs, ongoing);
• in the matter of the deceased estate of Dermot Mark Peterson [2026] SCV (Informal will, probate, ongoing)
• Susman v Lindy Allen (as Executor of the Estate of Andrew Roderick Fraser) [2025] SCVCA, S EAPCI 2025 0102 (Appeal, Recusal);
• In the Matter of Think Biggish Pty Ltd [2025] SCV S ECI 2020 00556, Unreported (Recusal application);
• Sulejman v Felsage Pty Ltd & Ors [2025] SCV (Trusts, opression, probate, equity - ongoing);
• Baamm Pty Ltd v Sulejman [2025] SCV S ECI 2025 04843, Unreported (Application to release property);
• Hu v Xie & Ors [2025] CCV (Joint Venture, fraud, constructive trust -ongoing);
• In the Matter of the Estate of Mizzi [2025] SCV, Part IV Application - resolved at mediation.
• Ball & Doggett v Coniglio Enterprises Pty Ltd & Ors [2024] VSC ( misleading and deceptive conduct, breach of warranty, restraints; employer poaching - resolved).
• Molawin Creek Ventures Pty Ltd & Ors v Sackl & Ors [2024] CCV (Breach of scientific consulting agreement; misleading and deceptive conduct);
• Hasslinger & Anor v Walter & Pearce Webster Dugdales [2024] VSC ( professional negligence, equity;  resolved);
• Nu Value Homes Pty Ltd (ACN 616 988 268( In Winding Up) v Cahill & Ors [2024] CCV, (for the insurer, building costs recovery);
• Nu Value Homes Pty Ltd (ACN 616 988 268( In Winding Up) v Martin & Ors [2024] VCAT (for the insurer, building costs recovery);
• Wang v Holiiez Investment Group Pty Ltd & Ors [2023] CCV (Building contract, misleading & deceptive conduct, tort of deceit; statutory interpretation, resolved at mediation) .
• Mutton (liquidator) v De Matteis, In the matter of de Matteis Pty Ltd (in liq)(set aside application)  [2023] FCA 1649
• Wang v  UD & C Urban Design & Ors  [2023] CCV (for the Plaintiff, construction contract, professional negligence, ongoing).
• Gunawan & Chandra v VMIA [2023] CCV (Insurance recovery action).
• Re Estate of L Kosta [2023] VSC (Wills & Deceased estate, dispute rightful executor).
• Energy Australia Pty Ltd v Ivanhoe Ops Pty Ltd [2022] CCV (for the Plaintiff, breach of energy supply)
• Baracon Builders Pty Ltd v Simon and Mary Zannis [2022] VCAT BP694/2020 (For the respondent, security for costs application).
• Re Jackanic & Jackanic v Stranscak [2022] VSC (Wills & Deceased estate - Part IV Application - resolved)
• Wegner & Anor v Mayberry & Anor  [2020] VSC 239 (Urgent application for caveat removal, unled).
• Andonov v Stojanovksi  [2020] VCC 266 (Statute of limitations).
• Happy Homes Building Group Pty Ltd v Registrar of Titles Victoria & Ors [2020] VCC 433 (Security for costs application, unled).
• Martin Builders Pty Ltd v Kane Worthy Constructions Pty Ltd [2020] (VCAT) Joint Venture contractual building dispute, unled, resolved at mediation).
• Acting for international company in an intellectual property dispute concerning misuse of proprietary imagery (FCA, unled, resolved by consent);
• Proceedings at VCAT including: a five day hearing for claim for loss and damage against guarantors under the Retail Leases Act 2003 (Vic) involving an allegation of fraud with expert handwriting evidence (unled);

Public & Administrative Law

• Dalton v Attorney General for the Commonwealth of Australia [2025] FCA 625 Horan J, (Judicial review application, Crimes Act 1918 (Cth)).
• Dalton v Attorney General for the Commonwealth of Australia (No.2) [2025] FCA 718, Horan J, (Costs).
• Advising practitioners on breaches of legal professional duties brought to Victorian Legal Services Board + Commissioner (ongoing);
• Chen ats Victorian Property Fund / Consumer Affairs Victoria/Department of Government Sevices [2025] (Advice - compensation recovery for defalcation of significant trust funds by agent, ongoing);
• Lo v Minister for Immigration & Citizenship  [2025] AAT 2025/3452 (Merits Review character cancellation).
• MCC v Jing Ju Pty Ltd & Ors [2025] CCV, Judge Rozen. Appeal under Food Act 1984 (Vic); Successful removal of Directors conviction with  substantially reduced penalty;
• CEO Department of Health v KMD & Ors, [2024] HCASL 271 - Stay & special leave application HCA  (led by Emrys Nekvapil SC);
• CEO Department of Health v KMD & Ors, [2024] NTCCA 8 (Judicial review, operation of Custodial Supervision Order,  led by Emrys Nekvapil SC);
• Karmo Cars Pty Ltd & Ors v VicRoads & Ors [2024] (advice, Judicial Review)
• Greyhound Racing Victoria v Kipirtidis, [2024] VRT (Reported) (Victorian Racing Tribunal, illegal substances, for GRV);
• Advising a large organization on the operation and their specific obligations under the Privacy Act 1988 (Cth) and the Privacy and Data Protection Act 2014 (Vic);
• applications for review under the Migration Act 1953 (Cth) including:
  • NDBR v Minister for Home Affairs & Anor [2021] FCAFC 170 (Judicial review of decision under s 501 Migration Act (Cth) led by Guy Gilbert SC for the Appellant);
  • Pereira v Minister for Immigration, Citizenship, Migrant Services and Multicultural Affairs [2022] AAT (restricted) (s501 visa cancellation overturned);
  • Niu v Minister for Immigration, Citizenship, Migrant Services and Multicultural Affairs [2023] AAT (s 501 visa cancellation, Obtain financial benefit by deception - $9m );
  • Kumar v Minister for Immigration, Citizenship, Migrant Services and Multicultural Affairs [2023] FCFCOA (Skilled visa cancellation);
  • Moana v Minister for Immigration and Border Protection (No 3) [2019} FCA 2052  (jurisdiction of Court, contempt).
• Lim v  Big Watermelon Bushy Park Pty Ltd  FCC [2022](General protection claim).
• Duran, Aftabzedeh & Zheng v Max Therapy Holdings Pty Ltd FCC [2022] ( Underpayment; sham contracting claim).
• Aun v KDRF Holding Pty Ltd & Ors  MLG1120/2019 FCC (Underpayment. claim).
• Lah v State of Victoria [2022] CI-22-00364 (police action, Intentional torts, resolved at mediation).
• Mead & Brotherton v State of Victoria [2023] CI-22-00691 (police action, Intentional tort).
• applications for review of decisions at the AAT, for example, under A New Tax System (Family Assistance)(Administration) Act 1999 (Cth); Income Tax Assessment Act 1936; the Paid Parental Leave Act 2010 (Cth; VCAT, and for example, VicRoads, Safe Transport Victoria.

Environmental & Planning Law

• Advise on Manura Conservancy Consitution and DGR status (with Biodiversity Legacy);
• HVP Plantations Pty Ltd v South Gippsland Shire Council (Gippsland Forest Guardians Inc) [2025] VCAT (FOI merits review of access to timber harvesting plan & audit report; applicant withdrew day prior to hearing. Documents released);
• HVP Plantations Pty Ltd v South Gippsland Shire Council (Hiscock) [2025] Z527 &  Z1056 VCAT (FOI merits review)(ongoing);
• Loughran v Department Energy, Environment Climate Action [2025) (Tort - negligence & nuisance - ongoing).
• Advising in relation to illegal land clearing & operation of EPBC Act (East Gippsland);
• Advising community organisations on Victorian bushfire ‘stay & go advice’ (led by Michael Wyles KC and other co-counsel);
• Advising and appearing in relation to various planning (applicant & developer) matters.

Memberships

• The Commercial Bar Association
• Migration Law Bar Association
• International Advocacy Training Committee
• Climate Change Section (Secretary), Commercial Bar