Toronto’s top oil and gas lawyers

Get to know Toronto’s top oil and gas lawyers from the results of Lexpert’s comprehensive annual peer review

Get to know Toronto’s top oil and gas lawyers from the results of Lexpert’s comprehensive annual peer review. The full list of Ontario’s most recommended energy lawyers and law firms can be found on our practice area rankings.

Oil and gas law is the branch of the legal profession that governs oil and gas production. In the survey, the practice encompasses all areas of upstream and downstream work, including exploration, construction, financing, taxation, environmental approvals, joint ventures and syndication, and federal and provincial regulatory applications.

Consistently recommended oil and gas lawyers

Vivek Bakshi

Law firm: Dentons Canada LLP

Year called to the Bar: 2009 (ON); 2000 (England & Wales)

Vivek Bakshi is a partner at Dentons Canada LLP. He represents clients in the energy, natural resources and infrastructure sectors, and is recognized as one of the country’s best oil and gas lawyers. Bakshi specializes in the structuring, negotiation and documentation of natural resource projects and related financings and in domestic and cross-border mergers and acquisitions in the oil, gas, water and power sectors. He previously practised at a leading English law firm in its London and Tokyo offices and has considerable international experience in Europe, the Middle East, Southeast Asia and the Far East. Bakshi also boasts extensive experience in regulated electricity markets and has acted for numerous clients in the development, operation and acquisition of independent power projects. He has also acted for sponsors, developers, offtakers and service providers in a range of natural resource projects. In the oil and gas sector, Bakshi has led transactions involving on and offshore petroleum development and has many years of experience in each link in the LNG value chain, having acted for developers of liquefaction facilities, LNG buyers and sellers and in connection with regasification terminal capacity rights.

Read more about Dentons Canada LLP on Indigenous consultation standards

Frederick D. Cass

Law firm: Aird & Berlis LLP

Year called to the Bar: 1980

Frederick D. Cass is a partner and co-chair of the energy group at Aird & Berlis LLP. He is also a member of the firm’s litigation group. Cass has been practising in the energy and energy regulatory fields for more than three decades. He is actively sought by participants in regulatory proceedings to provide advice on policy and strategy. Cass has appeared at all levels of the Ontario courts, at the Supreme Court of Canada and before the Ontario Energy Board in a wide variety of proceedings, including rate cases, facilities cases, system expansion cases and generic hearings. He has also appeared as counsel before the National Energy Board. Cass has authored and co-authored several books on energy law. He is considered among the top oil and gas lawyers in Canada.

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Lisa (Elisabeth) DeMarco

Law firm: DeMarco Allan LLP

Year called to the Bar: 1997 (ON); 2012 (England & Wales)

Lisa DeMarco is a senior partner at DeMarco Allan LLP. She is recognized as an expert in Canadian and international climate and energy law and consistently ranked as among the country’s leading oil and gas lawyers. DeMarco has more than two decades of experience in law, regulation, policy and advocacy relating to oil, gas, power and all aspects of climate change. She represents governments and leading energy companies in a wide variety of natural gas, electricity, pipeline and energy storage matters before various regulatory agencies, including the Ontario and National Energy Boards. DeMarco also assists Canadian energy companies and Indigenous business organizations on various domestic and overseas energy projects, sustainable and climate finance transactions, carbon capture and storage, climate-related financial disclosure, corporate climate risk, environmental and social governance, green bonds and sustainable business strategy. She plays an active role in the development of energy and greenhouse gas emissions law and policy throughout Canada and internationally. DeMarco is a member of the boards of directors of the Advanced Energy Centre and the International Emissions Trading Association.

Charles Keizer

Law firm: Torys LLP

Year called to the Bar: 1993

Charles Keizer is a partner and co-head of the infrastructure and energy practice at Torys LLP. He specializes in administrative, corporate and commercial law in the energy sector. Keizer advises energy sector participants, including renewable and conventional generators, transmitters, distributors, and gas and power marketers. He also advises clients on financing, project development, regulatory and contractual matters. Keizer has provided strategic advice related to federal and provincial regulatory regimes and has a strong understanding of project development, from the initial stages to connection and commercial operation. He regularly appears before the Ontario Energy Board on rates, licensing and leave to construct matters. Keizer is recognized as one of the best oil and gas lawyers in Canada.

Read more about Torys LLP on renewable energy sources

Ian A. Mondrow

Law firm: Gowling WLG

Year called to the Bar: 1991

Ian A. Mondrow leads the energy regulation and policy practice at Gowling WLG’s Toronto office, where he also serves as partner. Mondrow represents electricity generators, transmitters and distributors, natural gas shippers, competitive energy services providers, and large electricity and natural gas consumers before the Ontario Energy Board, the National Energy Board and in other Canadian regulatory forums. He advises government agencies and non-government organizations on energy policy and energy sector design and legislation in various national and international jurisdictions. His areas of expertise include energy policy, regulatory policy and processes, rates and tariffs, leaves to construct, compliance and licensing. Prior to joining Gowling, Mondrow served as a special advisor to the chair of the Ontario Energy Board and as vice-president of government and regulatory affairs at a major integrated energy retail and solutions company. He is considered among the top oil and gas lawyers in Canada.

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George Vegh

Law firm: McCarthy Tétrault LLP

Year called to the Bar: 1991

George Vegh is the head of the energy regulation practice at McCarthy Tétrault LLP’s Toronto office, where he also serves as counsel. He provides advocacy and advisory services to private and public sector clients. Vegh focuses on regulatory and wholesale market governance in the energy sector. He has extensive experience in working with market participants to address the impacts of federal and provincial climate change regulation. Prior to joining McCarthy Tétrault, Vegh was general counsel at the Ontario Energy Board. He is a leader in the energy sector, having served as chair of the Ontario Energy Association and the IESO Market Forum. Vegh currently serves as vice-chair of the Board of the Association of Power Producers of Ontario. He is recognized as among the country’s leading oil and gas lawyers.

Read more about McCarthy Tétrault LLP on legislative and policy shifts in climate change environmental regimes

Sandra L. Walker

Law firm: Dentons Canada LLP

Year called to the Bar: 1988

Sandy L. Walker is a partner and co-chair at Dentons Canada LLP’s competition and foreign investment review group. She is recognized as one of the country’s leading competition and investment, and oil and gas lawyers. Walker devotes her practice to securing government approvals for mergers and acquisitions from the Competition Bureau, Investment Canada and other regulatory agencies. She also acts on national security review process on behalf of foreign investors, in both state-owned and private sectors. Walker also provides strategic advice to clients on compliance issues arising from pricing, distribution and trade practices. She represents clients in an array of industries, including financial services, technology, mining, oil and gas, power, automotive, media and entertainment, food and beverage, manufacturing, transportation and retail. Walker is a regular speaker on foreign investment and competition law topics.

Read more about Dentons Canada LLP on financing the mining sector

Repeatedly recommended oil and gas lawyers

Heidi Clark

Law firm: Dentons Canada LLP

Year called to the Bar: 1998

Heidi Clark is a partner and department manager at the banking and finance group at Dentons Canada LLP’s Toronto office. Her practice includes advising domestic and foreign financial institutions, institutional investors, corporate and institutional borrowers and governments on a broad range of complex and structured financing transactions. Clark regularly advises clients in the areas of cross-border multi-currency transactions, syndicated financing, acquisition financing, alternative finance projects of public-private partnerships and project financing, asset-based lending, real estate and mortgage bond financing, aircraft financing and leasing. She is considered among the top oil and gas lawyers in Canada.


Christopher W. Langdon

Law firm: McCarthy Tétrault LLP

Year called to the Bar: 1999 (ON); 2001 (England & Wales)

Christopher W. Langdon is a partner at McCarthy Tétrault LLP’s offices in Toronto and London, UK. He also co-leads the firm’s projects group. Langdon devotes his practice to mining, oil and gas, infrastructure and power. He advises clients on project development and finance transactions, representing sponsors, project companies, commercial banks and international financial institutions. Langdon boasts extensive experience in banking, project finance, financial restructuring, streaming, joint ventures, off-takes and concessions. He also has broad international and cross-border experience touching more than 50 jurisdictions, having practised in the UK and the Middle East. Langdon is considered one of the best oil and gas lawyers in Canada.


Rocco M. Sebastiano

Law firm: Osler, Hoskin & Harcourt LLP

Year called to the Bar: 1994

Rocco M. Sebastiano is a partner at Osler, Hoskin & Harcourt LLP. He specializes in engineering, procurement and construction law. Sebastiano acts for project participants, including owners, governmental authorities, developers, contractors, operators, lenders, architects and engineers. He boasts extensive experience in public-private partnerships, privatizations and outsourcing of government services, procurements, project finance, major building, civil and public works design, engineering, construction, operation and maintenance. He also has deep experience in energy and infrastructure projects. Sebastiano’s practice includes contract negotiation with an emphasis on preventative structuring aimed at minimizing project risks and disputes. He is a qualified and experienced professional engineer and is considered one of Canada’s top oil and gas lawyers.


Crawford G. Smith

Law firm: Lax O'Sullivan Lisus Gottlieb LLP

Year called to the Bar: 1999

Crawford G. Smith is a partner at Lax O'Sullivan Lisus Gottlieb LLP. His litigation practice focuses on corporate and commercial matters, energy regulatory proceedings and securities, competition, public and administrative law and class action. He has appeared as counsel in all levels of court in Ontario, the Supreme Court of Canada, the Federal Court, commercial arbitrations and before a variety of administrative tribunals. Crawford’s energy practice involves economic issues in multi-party litigation. He frequently appears as counsel before the Energy Board at hearings regarding rate regulation, infrastructure development and demand-side management. He is considered among Canada’s leading oil and gas lawyers.