John Mather is a partner at DMG Advocates practicing commercial and public litigation.

John is adept on his feet in any setting. He regularly appears before the Ontario Superior Court and Court of Appeal. He has acted in numerous domestic and international arbitrations, including in New York and Riyadh, Saudi Arabia.

John has also appeared before various administrative tribunals and regulatory bodies.

John is an experienced public inquiry and commission lawyer. John currently acts as Commission Counsel for the Public Order Emergency Commission. The Commission, headed by Justice Paul Rouleau of the Ontario Court of Appeal, is inquiring into the circumstances that led to the Federal Government’s decision to invoke the Emergencies Act on February 14, 2022.

From 2019-2020, John served as Associate Commission Counsel to Associate Chief Justice Frank Marrocco at the Collingwood Judicial Inquiry, an extensive public inquiry that examined two major transactions undertaken by the Town of Collingwood. In 2021, John served as Duty Counsel to Ontario’s Long-Term Care COVID-19 Commission, assisting individuals who appeared before the Commission.

John has been recognized by Lexpert as a Leading Lawyer to Watch in corporate commercial litigation and has been featured in Benchmark Litigation’s 40 & Under Hot List for 2021 and 2022.

Prior to joining DMG Advocates in 2018, John spent five years as an associate lawyer at a leading national firm. John earned his law degree from Western University, where he graduated with Distinction. Prior to law, John worked as a journalist in Canada and the United Arab Emirates.

In addition to all types of general commercial litigation matters, John has experience in the following areas.

Product Liability, Automotive Law and Class Actions

John regularly acts for automobile manufacturers in product liability matters, including complex class actions. John also advises manufacturers on dealer relations and represents them in litigation and arbitration (including under the NADAP Rules).

Beyond the automotive industry, John also represents other designers and manufacturers in defence of a variety of product liability claims.

Public Inquiries, Regulatory Liability, Investigations and Inquests

John acts as both commission counsel and as counsel to participants and witnesses before public inquires and government commissions. His experience on both sides of an inquiry gives him unique perspective into the process, procedure and pressures of a public investigation. John is consistently recognized for his skill in analyzing and presenting evidence in complex and contentious matters.

John is similarly familiar with stresses of regulatory investigations and discipline proceedings. He regularly assists individuals and organizations in navigating these matters.

Commercial and International Arbitration

John has appeared as lead counsel in numerous commercial arbitrations, including ad hoc arbitrations and under institutional rules including ICC, UNCITRAL and JAMS. John’s arbitration experience includes urgent hearings for interim measures.

Injunctions and Urgent Proceedings

John has acted in numerous injunctions and urgent proceedings, including proceedings to evict trespassers and matters involving alleged breaches of confidentiality, non-competition and non-solicitation obligations. As part of this experience, John has successfully prosecuted contempt of court proceedings against parties that fail to comply with court orders.

Commercial Leasing, Construction and Condominium Law

John represents tenants and landlords in commercial leasing litigation and arbitration. John’s clients have included leading restaurant franchisors, real estate developers and office furniture manufacturers.

John regularly advises both condominium corporations and residents on their rights and obligations under Ontario’s Condominium Act.

John also handles construction disputes, including lien matters under Ontario’s Construction Act.

Cryptocurrency and Blockchain

John has represented clients in contractual disputes relating to the payment and transfer of cryptocurrency. John regularly advises clients on litigation risk and other aspects of dealing in cryptocurrency and blockchain technologies, including the sale and use of non-fungible tokens (or NFTs).

Media and Defamation

John regularly acts in defamation proceedings, including pursuing and defending anti-SLAPP motions. As a former journalist, John understands how the risk of litigation can affect reporting, editing and publishing decisions.

Procurement Litigation

John has acted in several procurement matters, both public and private. Among other cases, John acted for eHealth Ontario in complex litigation and arbitration relating to the government agency’s decision to terminate a multi-million dollar software development agreement.

Municipal procurement practices were also a focus of the Collingwood Judicial Inquiry, where John served as Associate Commission Counsel. John advises and represents unsuccessful RFP proponents.

Cross Border Litigation

John assists US counsel with a variety of cross-border litigation matter. John regularly works cooperatively with US counsel in cross-border class action proceedings. Among other services, John can also assist in obtaining the evidence of individuals or organizations located in Ontario.

Bar Admission

  • Ontario (2013)


  • Juris Doctor (with Distinction), Western University (2012)
  • Bachelor of Journalism (Honours), Ryerson University (2007)
  • The Advocates’ Society
  • Ontario Bar Association
  • Toronto Lawyers Association
  • Canadian Defence Lawyers
  • Defense Research Institute (DRI)
  • Benchmark Litigation (2021-2022)
    Future Star
  • Benchmark Litigation (2021-2022)
    40 & Under Hot List
  • Canadian Legal Lexpert Directory (2022)
    Leading Lawyers to Watch: Litigation – Corporate Commerial