Overview

Bar Admission: Alberta, 1995 | Ontario, 2001 | British Columbia, 2015
Maureen is the firm’s national Co-Chair and a member of the firm’s Partnership Board. Maureen practices out of both our Vancouver and Calgary offices and is the former Managing Partner of Osler’s Calgary office (2011–2017). Maureen’s litigation practice is national in scope; she is a trusted advisor to significant corporate clients and represents their interests in virtually every province and court in Canada.
Maureen is recognized for her leading expertise in “bet the company” litigation including, commercial, resource, constitutional, aboriginal and administrative law. She is a seasoned trial and appeal lawyer with extensive experience in commercial arbitrations (domestic and international) and other forms of dispute resolution. Maureen routinely appears on matters of judicial review, regulatory appeal, and environmental, administrative, constitutional, Charter and indigenous claims in Federal and Provincial Courts across the country.
Among many other matters, Maureen acted as lead litigation counsel on the Trans Mountain Pipeline Expansion Project, successfully defending all regulatory appeals and judicial review applications as well as leading significant injunction and contempt proceedings.
Numerous industry publications describe Maureen as being widely regarded by clients and peers as one of Canada’s top litigators in the areas of energy & resource, indigenous, and commercial litigation, appellate advocacy, and constitutional and administrative law:
Benchmark Litigation notes that Maureen is described as: “a real force in the litigation community, taking charge and really appearing front and centre on big actions …” “She is very collaborative and really knows her stuff. She is very good at getting things under control.”
“Maureen speaks a language that everyone can understand, regardless of their experience.”
Chambers and Partners ranks Maureen as Band 1 in Commercial Litigation and describes Maureen as follows:
“… a very capable litigator … does a good job of moving matters forward.”
“Very responsive, very competent. eloquent in advocacy and gives good advice.“
“An excellent lawyer who can be tough and tactful simultaneously. She puts our interests first and finds a solution to meet the entire situation.“
“Consistently provides outstanding service and representation.”
“Maureen is excellent. She often thinks outside the box and provides sound, thoughtful and practical advice.”
Significant decision at the Supreme Court of Canada: five-judge majority finds the Impact Assessment Act unconstitutional
Trans Mountain Canada Inc. in its successful defence of four judicial review applications at the Federal Court of Appeal, challenging the June 2019 federal approval (Order in Council) of the Trans Mountain Pipeline Expansion Project
Supreme Court of Canada rules in favour of the Trans Mountain Expansion Project
Equinor Canada Limited and Husky Oil Operations Limited regarding commercial matters related to the potential Bay du Nord offshore oil project
Kinder Morgan Canada Limited in its litigation victories for the Trans Mountain Pipeline Expansion
Terra Nova Consortium in a challenge over its calculation of past and ongoing provincial royalties
National Energy Board Recommends Approval of the $6.8-billion Trans Mountain Expansion Project
Canada’s economic outlook 2026: trade, policy and what comes next.
The Building Canada Act (BCA) and Major Projects Office will change the process for approving and building key projects for Canada.
U.S. tariffs continue to pose challenges for the Canadian economy and President Donald Trump’s One Big Beautiful Bill Act threatens even further...
A recent SCC decision relating to interjurisdictional immunity is a welcome development for proponents of regulatory and jurisdictional certainty.
Osler is proud to announce that Brad Newby has assumed the role of Managing Partner of the firm’s Vancouver office, effective January 1, 2026.
This prestigious publication showcases leading litigators across Canada.
Félicitations à Maureen Killoran, c.r., pour sa nomination au palmarès 2025 des 25 avocats les plus influents de Canadian Lawyer.
Osler congratulates National Co-Chair Maureen Killoran, KC, and partners Mary Buttery, KC, Laura Fric and Teresa Tomchak on their recognition...

Practice Areas

• Alternative Dispute Resolution
• Environmental Law
• Civil Litigation
• Natural Resources & Energy
• Class Action Plaintiff

Bar Information

Called to the bar: 1995 (AB); 1995 (ON); 2013 (AB)