Mark Sheeley

Mark has a wide-ranging corporate-commercial litigation practice, with expertise in complex class action litigation and matters relating to securities, tax, insolvency, administrative law and internal investigations.

Mark is committed to client service, identifying and obtaining practical results that meet his clients’ objectives, whether in the courtroom or the boardroom. He has appeared before the Ontario Superior Court of Justice, Divisional Court, Supreme Court of British Columbia, Court of Appeal for British Columbia, Ontario Securities Commission, Tax Court of Canada and Federal Court of Appeal.

Representative Work

  • Fiera Foods Company

    Fiera Foods in its successful appeal from a Canada Revenue Agency ITC reassessment

  • TerraFarma

    TerraFarma in its up to $68 million acquisition by Aurora Cannabis

  • Cameco Corporation

    Cameco Corporation in its successful dismissal of CRA appeal by the Supreme Court of Canada


    • Cameco Corporation, in the precedent-setting trial of a transfer pricing dispute in the Tax Court of Canada relating to Cameco’s international sales structure, and the subsequent appeal to the Federal Court of Appeal.
    • Loblaw Companies Limited, in the precedent-setting trial of a tax dispute in the Tax Court of Canada relating to Loblaw’s international financial affiliate, and the subsequent successful appeal to the Federal Court of Appeal.
    • Canada Bread Company Limited, in an application for a stay of a decision of the Ontario Labour Relations Board.
    • Amex Bank of Canada, in a class action relating to prepaid financial products before the Supreme Court of British Columbia and Court of Appeal for British Columbia.
    • A multinational auto manufacturer, in regulatory investigations regarding emissions.
    • A secured creditor, in its successful application to obtain protection for a debtor under the Companies’ Creditors Arrangement Act before the Commercial List.
    • Magna International, in various commercial disputes.
    • NEC Corporation, in several competition class actions across Canada.
    • A Canadian financial institution, in a regulatory investigation and settlement.

    Latest Insights

    • Osler Update Feb 18, 2021

      Supreme Court denies Crown’s request for leave to appeal Cameco transfer pricing decision

      On February 18, 2021, the Supreme Court of Canada declined the Crown’s application seeking leave to appeal the June 2020 decision of the Federal Court...

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    • Osler Update Jun 29, 2020

      Federal Court of Appeal dismisses Crown’s appeal in Cameco

      The Federal Court of Appeal upheld the Tax Court’s decision that Cameco’s transactions with its Swiss subsidiary were on arm’s length terms and, there...

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      Federal Court of Appeal dismisses Crown’s appeal in Cameco

    Awards and Recognition

    • Top Appellant at the 2013 Bowman Tax Moot
    • Winner of the 2012 International Competition in Mediation Advocacy
    • Recipient of the Blake, Cassels & Graydon LLP Award, the Davies Ward Phillips & Vineberg LLP Award in Commercial Law, Business Associations and Tax, and the Borden Ladner Gervais LLP Professional Excellence Award

    Media Mentions

    • Osler News Feb 16, 2024

      Osler welcomes seven new partners and one new counsel in 2024

      Osler is pleased to announce the addition of seven new partners and one new counsel across our offices in Toronto, Montréal, Calgary and Vancouver, ef...

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    • Osler News Nov 7, 2022

      A fresh take on applying decision trees to case assessments in litigation

      Decision trees allow lawyers to explain a dispute visually, with easily digestible language and numbers. A single page can convey as much information ...

      Read more
    • Osler News May 12, 2021

      Osler’s National Litigation team recognized at the Benchmark Canada Awards 2021

      Osler is proud to announce that our National Litigation team has been recognized at the 2021 Benchmark Canada Awards.

      Read more

    Community Involvement

    • Osgoode Hall Mooting Society, Treasurer
    • Woodgreen Debt Clinic, Debt Advisor



    • Osgoode Hall Law School, J.D.
    • University of Western Ontario, M.A.
    • University of Victoria, B.Sc. (Hons.) (With Distinction)


    • English

    Professional Affiliations

    • Ontario Bar Association
    • Canadian Bar Association
    • Law Society of Ontario