Our Team

Dennis Mahony is the head of Torys’ Environmental, Health and Safety Practice Group, the Co-Chair of the firm's interdisciplinary Climate Change and Emissions Trading Practice and member of our Infrastructure and Energy Group.  

He is certified by the Law Society of Upper Canada as a Specialist in Environmental Law and has been recognized over the years as one of Canada's leading practitioners, including in: Lexpert/ALM’s Canadian Legal Lexpert Directory; Practical Law Company’s Which Lawyer? Yearbook; Woodward White’s Best Lawyers in Canada; Law Business Research’s International Who’s Who of Environment Lawyers; Real Time News' LawDay; and Legal Media Group’s Guide to the World’s Leading Environment Lawyers. Dennis is one of only 5 lawyers in Toronto that ranked in Chambers & Partners top rated environmental band for Canada. Dennis is also a past recipient of the Lexpert award for Canada’s Top 40 Lawyers Under 40. He is a past Co-Chair of the International Outreach Task Force of the American Bar Association’s Section of Environment, Energy and Resources (SEER), the current International Vice-Chair of the Energy and Environmental Markets and Finance Committee of SEER, and a Past Chair of the Canadian Bar Association’s National Environmental, Energy and Resources Law Section.

Dennis' environmental, health and safety practice involves work with a broad range of public and private sector clients, including public and private companies, federal government agencies, Crown corporations, provincial bodies and municipalities. He provides advice to corporate clients in virtually every industrial sector, including pulp and paper; mining; chemicals and plastics; energy; water and waste water treatment and disposal; manufacturing (including automotive, auto parts, adhesives, sports equipment, injection molding and food); financial institutions (including all of North America’s major banks); and real estate (including major property and property management corporations).

As part of his transactions practice, Dennis assists buyers, sellers, lenders and investors through all the environmental aspects of a transaction, from the design and coordination of deal-specific (often multiple-site, international) environmental liability assessments; through the negotiation of agreements; and in handling closing and post-closing details. In a typical year, the group is involved to varying degrees in more than 100 commercial transactions.

Dennis’ regulatory practice involves technical and strategic advice that spans the full range of issues in the environmental, health and safety field, including contaminated sites; federal and provincial environmental assessments and other approvals; quasi-criminal, civil and administrative liability assessments (including those related to government orders); transportation of dangerous goods and waste (domestically and internationally); climate change; general legal compliance; legislative initiatives; and Canada-U.S. cross-border issues.

Dennis' litigation related practice covers an equally broad range of issues, including environmental assessments, complex approval hearings, appeals of administrative orders, quasi-criminal defence work and civil litigation, much of which is with the group's full-time litigators.

Torys' cross-border Climate Change and Emissions Trading Practice brings deep business law expertise to the many challenges and opportunities related to global warming. Understanding that the implications of the movement extends to every aspect of modern business, the group is interdisciplinary, drawing on a wealth of top-ranked expertise in a variety of fields, including energy and infrastructure; environmental, health and safety; corporate/commercial; securities; mergers and acquisitions; project finance; institutional lending; financial institutions; intellectual property; pension and employment; real estate and infrastructure; trade; tax; and litigation and dispute resolution. Torys is one of only four law firms in Canada ranked in the top "highly recommended" category for its climate practice by the U.K.-based international ranking organization Practical Law Company.

Dennis’ climate change and emissions trading practice involves helping our clients navigate through this evolving, multi-faceted field, including keeping them informed on the numerous domestic and international developments in the area and working on project-specific teams for everything from assessing the ever evolving securities disclosure requirements to emissions trading. Recent engagements include acting for the seller in one of the first GHG trades under the new Alberta regime, which was also one of the largest emissions trades in Canada to date. Dennis is one of only five climate lawyers in Canada endorsed by Practical Law Company.