Diana Weir


[email protected]

Diana specializes in environmental law, offering legal and strategic advice on environmental matters related to Ontario, federal and municipal legislation.

Her practice includes obtaining environmental permits and authorizations, ensuring environmental compliance and acting as counsel on environmental aspects of business, such as due diligence in mergers and acquisitions.

Diana also has notable experience in litigation, defending clients charged with environmental and regulatory offences and conducting appeals of remediation orders. She frequently represents clients in environmental litigation claims before Ontario courts.


  • Advising a leading oil company in multiparty contaminated lands litigation.
  • Assists clients appealing to the Ontario Land Tribunal in relation to Ministry of the Environment, Conservation and Parks Director’s Orders.
  • Advising Plaintiffs and Defendants in multiple contaminated lands actions, bringing successful summary judgment motions to have actions dismissed based on the expiry of limitation periods.
  • Acted as counsel in Douglas v Stan Fergusson Fuels, 2016 ONSC 442 (Ontario Div Ct), 2018 ONCA 192 (Ont CA), leave to appeal to SCC refused [2018] SCC No 141.
  • Advising a chemical manufacturer on spill response and reporting to minimize the likelihood of charges.
  • Advising a fresh produce supply company regarding compliance with extended producer responsibility regimes in several jurisdictions.
  • Advising a multinational consumer healthcare company regarding new substances chemical compliance.
  • Advising on compliance with Regulation 347 relating to waste issues.
  • Advised Innergex Renewable Energy Inc. in its acquisition of a 60 MW solar portfolio located in Sault Ste. Marie, Ontario for a purchase price of $50.2 million, along with assumption of $169.5 million in debt.
  • Advised Thrust Capital Partners Fund I L.P. in their acquisition of an Ontario-based manufacturer of aerospace and satellite components.
  • Assisted Carlsberg Group in its acquisition by way of plan of arrangement of Waterloo Brewing Ltd. for $144 million all cash consideration.

Beyond Our Walls

Professional Involvement

  • Chair, Environmental Law Section Executive Committee, Ontario Bar Association
  • Member, Canadian Bar Association
  • Steering Committee Member, Cambridge Forum on Environmental Law 2nd Generation

Community Involvement

  • Volunteer, Pro Bono Ontario Free Legal Advice Hotline
  • Volunteer, Centre 55 Community Centre

Bar Admission & Education

  • Ontario, 2014
  • Certificate in ESG, Climate Risk and the Law, Osgoode Hall Law School (York University), 2023
  • JD, Queen's University, 2013
  • BA (Honours) (Faculty of Arts & Science), Queen's University, 2010