Deirdre A. Sheehan

Deirdre A. Sheehan

Partner, Regulatory, Indigenous and Environmental

Co-Chair: Regulatory, Indigenous and Environmental

Key Contact: Regulatory

Contact Information

tel: 403.260.7053



Bar Admission

Alberta, 2002


University of Victoria, LLB, 2001

University of Alberta, BEd, 1996



Deirdre is Co-Chair of Osler's Regulatory, Indigenous and Environmental practice. Deirdre practices energy regulatory, Indigenous and environmental law and advises clients on the regulatory and environmental aspects of power, electricity, oil and gas and other energy developments, including regulatory proceedings for setting rates and tariffs. She advises on power transmission, distribution and generation projects in Alberta and regularly appears on behalf of clients before the Alberta Utilities Commission. Deirdre also has experience with matters before the Alberta Energy Regulator, the Canada Energy Regulator and other regulatory agencies and tribunals, including Alberta Environment and Protected Areas, the Alberta Environmental Appeals Board, the British Columbia Utilities Commission and the Yukon Utilities Board.

Deirdre has advised on power transmission lines, renewable and other power generation, oil and gas wells, pipelines, oil sands developments, upgraders, gas storage, and waste disposal facilities. She also has widespread experience in environmental impact assessments required under provincial and federal laws.

Deirdre's Indigenous law practice focuses on consultation, accommodation and participation of Indigenous groups in relation to large energy projects.

Deirdre also teaches Administrative Law at the University of Calgary.

Prior to joining Osler, Deirdre was a partner at another leading national law firm.

  • Canada Growth Fund

    The Canada Growth Fund in its connection with its carbon credit offtake agreement and $200 million strategic investment in Entropy Inc.

  • *Prior to joining Osler:

    • ATCO Electric Ltd., in transmission tariff proceedings before the Alberta Utilities Commission
    • Undisclosed client, in Canada Energy Regulator gas export licensing requirements and related issues
    • ATCO Electric Ltd., on all facility approvals before the Alberta Utilities Commission for an 80-kilometer 240 kV transmission line
    • Various clients, in Alberta Energy Regulator related matters, including with respect to gas storage projects, waste disposal and facility approvals for sweet and sour gas facilities, and hydraulic fracturing
    • ATCO Gas, a performance-based ratemaking regulated utility, before the Alberta Utilities Commission in respect of capital costs adjustments to be reflected in rates for 2014 and 2015
    • Undisclosed client, in Canada Energy Regulator compliance and investigation matters
    • Undisclosed client, in Alberta Energy Regulator compliance and investigation matters
    • Lead Counsel to Alberta PowerLine LP, a transmission facility owner, on all facility approvals before the Alberta Utilities Commission for the Fort McMurray West 500-kV Transmission Project, designated as Critical Transmission Infrastructure between Edmonton and the Fort McMurray area of Alberta, including in respective of environmental impact assessment and Indigenous consultation issues
    • Yukon Electrical Company Limited, in regulatory approvals and re-licensing of a hydro project before the Yukon Water Board, including in respect of environmental impact assessment and Indigenous consultation issues
    • A large oil and gas producer regarding First Nations consultation in relation to energy project developments on reserve lands and traditional lands of various First Nations in Alberta and British Columbia
    • Undisclosed client, in regulatory approvals for a solar project in Alberta
    • ATCO Utilities, in proceedings to establish the 2018-2020 Generic Cost of Capital for Alberta-based regulated utilities
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  • Chambers Canada: Canada’s Leading Lawyers for Business: Recognized in Energy: Power (Regulatory)
    • "Deirdre is extremely knowledgeable and provides practical advice and guidance."
    • "She looks at issues in a strategic manner and understands the commercial implications."
    • "Deirdre provides smart and insightful support that is well thought out and reasoned - I can count on her for fantastic analysis."
  • Legal 500: Recognized in Aboriginal Law, Energy and Natural Resources (Power)
  • The Canadian Legal Lexpert Directory: Recognized in Aboriginal Law, Energy (Electricity), Energy (Oil & Gas)

  • Law Society of Alberta
  • Canadian Bar Association (Administrative Law, Alberta South, Executive Member)

  • First Nations increasingly moving from accommodation to equity and shared ownership:  On energy projects, courts are putting new spin on the duty to consult, Lexpert (October 5, 2022)
  • Ermineskin decision involving Coalspur mine adds novel twist to the duty to consult, by David Bursey and Deirdre Sheehan, Canadian Mining Journal (October 8, 2021)
  • Limiting the right to procedural fairness: New Alberta regime expands administrative powers and penalties (Deirdre Sheehan, Brynne Harding, Patrick Schembri (26 may 2021)
  • "Environmental and Regulatory Issues during the COVID-19 Pandemic", presentation to the CBA Environmental Law Section South (April 20, 2020)