Teresa Tomchak*

A partner in the Litigation Group of our Vancouver office, Teresa’s practice focuses on securities litigation and regulation. With more than 20 years of experience, she has worked on multiple shareholder disputes, hostile take-over bids and proxy fights as well as contested plans of arrangement. Teresa’s practice also includes securities class action defence.

Teresa’s practice includes securities regulatory matters, where she has represented clients during investigations and enforcement hearings before various provincial securities commissions, which have included allegations of insider trading, illegal distributions, market manipulation, discretionary trading, suitability matters and fraud. She consistently works with registration requirements under securities legislation with respect to trading in securities.

She has advised special committees during transactional matters and internal investigations, including whistleblower complaints as well as financial institutions and investment advisors, including in broker-dealer litigation.

Prior to joining Osler, Teresa was a partner at a leading regional law firm.

Representative Work

  • Xos

    Xos in its business combination with ElectraMeccanica

  • Boart Longyear Company

    Boart Longyear in the sale of its shares to American Industrial Partners Capital Fund

  • Aimia Inc.

    Lead investor in its strategic placement in Aimia

  • Mind Medicine

    Mind Medicine in its successful proxy contest against FCM MM Holdings, LLC

Prior to joining Osler:
  • Representing Peter Smith, a shareholder, director and former CEO in challenging approval of a plan of arrangement before the TSX Venture Exchange and in court proceedings during a proxy fight relating to procedures for an AGM and proxy voting 2021 BCSC 1758.
  • Representing the TSX Venture Exchange in successfully maintaining its decision from a hearing and review before the British Columbia Securities Commission regarding the suitability of a director 2021 BCSECCOM 79.
  • Representing four of the 65 respondents named in a matter before the British Columbia Securities Commission relating to an alleged misuse of prospectus exemptions contrary to the public interest, from which there is a related challenge to the constitutionality of the freeze order section of the Securities Act, and a related class action, Bridgemark Financial Corp. 2019 BCSECCOM 14, 2019 BCSECCOM 191, 2020 BCSC 527, 2020 BCCA 301, 2020 BCSC 1704, 2021 BCSC 1459
  • Representing Keith Piggott, a shareholder, director and former CEO in successfully opposing a plan of arrangement proposed by Core Gold Inc.2019 BCSC 1267.
  • Representing WesternOne Inc and its directors and officers in defending a securities class action relating to primary and secondary market disclosure in Ontario 2015 ONSC 7313 and 2018 ONSC 4794.
  • Representing Shair.com Digital Services Inc. in a proceeding involving the misappropriation of cryptocurrencies 2018 BCSC 1512
  • Representing Paul Oei and other corporate entities in a hearing before the BC Securities Commission relating to fraud allegations Oei 2017 BCSECCOM 365 and 2018 BCSECCOM 231
  • Representing Amber Capital LP and Paulson & Co Inc., the two largest shareholders of Eco Oro Minerals in the courts of British Columbia during two oppression proceedings during a proxy fight 2017 BCSC 664 and 2017 BCSC 669 and 2017 BCSC 988 including an appeal 2017 BCCA 244, and before the Ontario Securities Commission on an appeal from a decision of the TSX approving a share issuance 2017 ONSEC 23.
  • Advising the special committee of Whistler Blackcomb in its $1.4. billion acquisition by Vail Resorts
  • Representing Red Eagle Mining Corporation in its hostile take-over for CB Gold, in which the BC Securities Commission refused to apply proposed amendments to the take-over bid regime and issued a cease trade order over CB Gold’s poison pill 2015 BCSECCOM 401.
  • Representing United Flower Growers Co-Operative Association in obtaining approval of a contested plan of arrangement 2015 BCSC 1169, which considered the applicability of the BC Business Corporations Act to a co-operative and the fairness of the arrangement in the absence of dissent rights and a fairness opinion.
  • Representing Coast Wholesale Appliances Inc. in defending a hostile take-over by CWAL Investments Ltd. resulting in a settlement the day prior to the hearing to cease trade the poison pill (2014).
  • Representing Huntingdon Capital Corp in its hostile takeover bid of KEYreit, which resulted in the first decision of a securities commission to consider the appropriate jurisdiction in which to bring an application to cease trade a poison pill. 2013 BCSCECOM 64 and OSC March 14, 2013.
  • Representing Northern Minerals Investment Corp. in a proxy battle to replace the board of Mundoro Capital Inc. resulting in the first court decision regarding the validity of an advance notice policy 2012 BCSC 1090.
  • Representing Oliver-Lennox King in his successful proxy fight for Roxgold Inc. (2012)
  • Representing MacDonald, Dettwiler and Associates Ltd. in the first class action in Canada to deny leave under the secondary market provisions of the Securities Act and the successful defence of the appeal 2011 BCSC 1416 and 2012 BCCA 456.
  • Representing entities controlled by Carl Icahn in successfully obtaining orders to cease trade poison pills and a successful defence of an appeal from the same resulting in the first decision of an appellate court the validity of a poison pill, during an $800 million hostile takeover bid for Lions Gate Entertainment Corp 2010 BCCA 231; 2010 BCSECCOM 629 as well as a related oppression action during a proxy fight 2010 BCSC 1547 and 2011 BCCA 228.

Latest Insights

  • Podcast Apr 1, 2024

    Trends in shareholder activism

    In this episode of the podcast, guest host Teresa Tomchak, a partner in the litigation group at Osler, and David Salmon, President of Laurel Hill Cana...

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    Trends in shareholder activism
  • Osler Update Mar 11, 2024

    Ontario Capital Markets Tribunal clarifies considerations for a private placement in the face of an unsolicited takeover bid in Aimia

    The OSC has provided helpful guidance in assessing whether a private placement undertaken in the face of a take-over bid is an improper defensive tact...

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    Ontario Capital Markets Tribunal clarifies considerations for a private placement in the face of an unsolicited takeover bid in Aimia
  • Blog Jan 24, 2024

    Duty of procedural fairness that would be owed to witnesses in issuing summonses under the Securities Act is minimal

    A recent British Columbia Court of Appeal decision confirmed that, amongst the very limited avenues that witnesses have to challenge a regulatory inve...

    Read more
    Duty of procedural fairness that would be owed to witnesses in issuing summonses under the Securities Act is minimal
  • Video Jan 17, 2024

    ESG and shareholder activism: key tips for issuers

    Shareholder activism is on the rise in Canada. Investors are closely monitoring environmental, social and governance (ESG) related disclosure, posing ...

    Read more
    ESG and shareholder activism: key tips for issuers
View all Insights

Awards and Recognition

  • Chambers Canada: Canada’s Leading Lawyers for Business: Recognized in Securities Litigation
  • Best Lawyers in Canada: Recognized in Securities Law
  • Benchmark Litigation Canada: Recognized in “Top 100 Women in Litigation” in Canada
  • Lexpert Special Edition – Litigation: Recognized as a Leader

Media Mentions

  • Osler News Nov 23, 2023

    23 Osler lawyers recognized in Lexpert Special Edition: Litigation 2023

    23 Osler lawyers featured in the Lexpert Special Edition: Litigation 2023.

    Read more
  • Osler News Aug 3, 2023

    Four Osler partners recognized in Benchmark Canada’s ‘Top 100 Women in Litigation’

    Osler congratulates partners Maureen Killoran, KC, Mary Buttery, KC, Teresa Tomchak and Laura Fric for their inclusion in the Benchmark Canada’s Top 1...

    Read more
  • Osler News Apr 3, 2023

    Teresa Tomchak joins Osler’s Litigation practice in Vancouver

    We welcome Teresa Tomchak to Osler’s Litigation team in Vancouver. Teresa’s practice is focused on securities litigation and regulation, as well as se...

    Read more

Community Involvement

  • CBA’s WLF Mentoring Program, Mentor
  • Vancouver International Marathon Society (RUNVAN), Director, Chair of HR & Governance Committee

Speaking and Writing

Published Work


Recent Trends in Securities Litigation: Canadian Bar Association Securities Section, Vancouver, March 9, 2023

Securities Litigation Update: Pipestone Conference, Lake Louise, September 22, 2022

Shareholder Activism: CLEBC Advanced Securities Law, Vancouver, May 10, 2022



ESG and Shareholder Rights: how activist investors are shaping the corporate world like never before, Lexpert Legal Insights, August 22, 2022

Corporate civil wars: How activist shareholders are influencing Canada’s Companies, Lexpert Legal Insights, Jul. 28, 2021



  • University of British Columbia, LL.B.
  • University of Alberta, B.Comm. (with distinction)


  • English

Professional Affiliations

  • Law Society of British Columbia
  • Canadian Bar Association, multiple sections including the securities sub-section
  • Prospectors and Developers Association of Canada
  • The Advocates’ Society
  • Womens’ White Collar Defence Association
  • Commercial Bar Association (COMBAR)