Recognition | 04 September 2025
Best Lawyers in Canada 2026: 36 of our Lawyers Recognized Once Again
Montréal, September 4, 2025 – We are pleased to announce that 36 lawyers at De Grandpré Chait are featured in the 2026 edition of Best Lawyer...
Sébastien Poirier
PartnerSébastien Poirier is a lawyer in public real estate law, environmental law, and administrative law at De Grandpré Chait. He advises and represents businesses, property owners, real estate developers and builders, as well as individuals in their dealings with municipal authorities or government bodies, and in matters involving the laws and regulations they are responsible for enforcing. His expertise covers the entire life cycle of real estate and development projects, from strategic planning to dispute resolution.
His practice is diverse and includes, in particular, urban planning and land use planning, the management and rehabilitation of contaminated sites, applications for authorization to use land in agricultural zones, the operation of quarries and sand pits, expropriation proceedings, and regulations concerning wetlands and bodies of water. He also has recognized expertise in constitutional issues arising from the application of municipal and provincial regulations to federally regulated businesses.
Sébastien favours a logical, rigorous, and pragmatic approach focused on results. He analyzes each matter with precision in order to provide his clients with a realistic assessment of the legal issues, risks, and strategies available to achieve their objectives.
While he favours the prevention and amicable resolution of disputes whenever possible, Sébastien also has solid litigation experience and regularly represents his clients before Québec’s judicial and administrative tribunals, including the Québec Court of Appeal, the Superior Court of Québec, the Court of Québec, the Administrative Tribunal of Québec (TAQ), and the Commission de protection du territoire agricole du Québec (CPTAQ).
Sébastien is the author of several publications and conference papers in environmental law, constitutional law, and expropriation law. He notably contributed to an in-depth study on the scope of Québec’s and municipalities’ constitutional jurisdiction in environmental matters. His work has been cited on several occasions by courts in expropriation matters, including the Québec Court of Appeal.
Sébastien Poirier is a lawyer in public real estate law, environmental law, and administrative law at De Grandpré Chait. He advises and represents businesses, property owners, real estate developers and builders, as well as individuals in their dealings with municipal authorities or government bodies, and in matters involving the laws and regulations they are responsible for enforcing. His expertise covers the entire life cycle of real estate and development projects, from strategic planning to dispute resolution.
His practice is diverse and includes, in particular, urban planning and land use planning, the management and rehabilitation of contaminated sites, applications for authorization to use land in agricultural zones, the operation of quarries and sand pits, expropriation proceedings, and regulations concerning wetlands and bodies of water. He also has recognized expertise in constitutional issues arising from the application of municipal and provincial regulations to federally regulated businesses.
Sébastien favours a logical, rigorous, and pragmatic approach focused on results. He analyzes each matter with precision in order to provide his clients with a realistic assessment of the legal issues, risks, and strategies available to achieve their objectives.
While he favours the prevention and amicable resolution of disputes whenever possible, Sébastien also has solid litigation experience and regularly represents his clients before Québec’s judicial and administrative tribunals, including the Québec Court of Appeal, the Superior Court of Québec, the Court of Québec, the Administrative Tribunal of Québec (TAQ), and the Commission de protection du territoire agricole du Québec (CPTAQ).
Sébastien is the author of several publications and conference papers in environmental law, constitutional law, and expropriation law. He notably contributed to an in-depth study on the scope of Québec’s and municipalities’ constitutional jurisdiction in environmental matters. His work has been cited on several occasions by courts in expropriation matters, including the Québec Court of Appeal.
Field of practice
Best Lawyers in Canada® – Ones to Watch Environmental Law – 2026
Expropriation in Quebec and Ontario: Changes to the Landscape for Owners in Light of Quebec’s Bill 22, Sébastien Poirier and Sarah Spitz, Recent Developments in Environmental Law (2024), Volume 561, Quebec Bar’s Professional Quality Service.
Federalism and Environment in Quebec: Towards the Creation of Federal Enclaves? David Robitaille and Sébastien Poirier, Recent Developments in Environmental Law (2020), Volume 483, Quebec Bar’s Professional Quality Service.
The Impact of Urban Planning Regulations on the Main Compensation in Expropriation Matters, Sébastien Poirier, with the collaboration of Camille Ingarao, Recent Developments in Expropriation Law (2020), Volume 481, Quebec Bar’s Professional Quality Service.
Accessory Compensation in Expropriation Matters: Is Your Damage Direct or Indirect? Louis Beauregard and Sébastien Poirier, Recent Developments in Expropriation Law (2019), Volume 462, Quebec Bar’s Professional Quality Service.
Federal Competencies and the Application of Provincial Environmental Regulations and Laws: A Turbulent Relationship, Sébastien Poirier and Roger Paiement, Recent Developments in Environmental Law 2018, Volume 450, Quebec Bar’s Professional Quality Service.
The Scope of Quebec’s Constitutional Competence in Environment: A Look at the Issue of Interprovincial Transport of Hydrocarbons, Sébastien Poirier, David Robitaille, and Stéphanie Roy, IRAI, Study No. 2, 2018.
Transportation of Hydrocarbons: Legal and Political Issues, Training for the Montreal Regional Association of Quebec Solidaire, February 25, 2017.
The Application of the Precautionary Principle under Article 20 in fine of the Environment Quality Act: A Wide Open Door, Sébastien Poirier, RJEUM, Volume 2, Number 1, 2016.
LL.B.
Université de Montréal, 2015
Master of Arts in Philosophy University of Montreal, M.A., 2011
Bachelor of Science / Major in Psychology and Minor in Philosophy University of Montreal, B.Sc., 2009
Member, Barreau du Québec
Member, Canadian Bar Association – Québec
Member, Institut de développement urbain du Québec
Co-founder and Editor-in-chief, from 2013 to 2015
Student Legal Journal of the University of Montreal
University of Montreal, Faculty of Law
Pro Bono Intern, from 2013 to 2014
PBSC, University of Montreal section
Hochelaga-Maisonneuve Community Education Pavilion
Volunteer in the Psychiatry Department, from 2012 to 2015
Maisonneuve-Rosemont Hospital
