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Sidonia J. Tomasella

Partner Admitted to the Ontario Bar: 2009

Sidonia offers her municipal and land use planning clients a unique value proposition. In addition to her legal experience, her previous career as a land use planner gives her clients the added benefit of understanding the technical aspects of land development which, along with her time at the City of Toronto’s Legal Division and at the Ontario Ministry of Municipal Affairs and Housing, also provides excellent insight to the decision-making process. She is dedicated and passionate about making a meaningful contribution not only to her clients’ files, but to the development of communities. 

Sidonia is a member of the firm's Municipal & Land Use Planning Group and Chair of the firm's Associates Committee. She assists private and public sector clients through the development and application process, from pre-consultation with various city departments to representation before the courts and various municipal authorities and administrative tribunals, including the Ontario Land Tribunal (formerly the Local Planning Appeal Tribunal).

Early in her career at the firm, Sidonia was seconded to the City of Toronto’s Legal Division (Planning and Administrative Tribunal Law section). Before beginning her legal practice, she was a senior land use planner and a municipal policy advisor for the Ontario Ministry of Municipal Affairs and Housing, where she was involved in a number of government initiatives related to land use planning, municipal governance and housing. Sidonia also lectures on land use planning matters at Ryerson University to students of the University’s Urban and Regional Planning Undergraduate Program.

Awards & Recognition

  • Recognized in The Best Lawyers in Canada in the field of Municipal Law

Professional Involvement


  • Urban Land Institute

Teaching Engagements

  • Instructor, "Land Use Planning Law," School of Urban and Regional Planning, Ryerson University, 2013.

Selected Speaking Engagements

"GTAA Inclusionary Zoning Webinar," Co-presenter with Tom Halinski, Greater Toronto Apartment Association, November 2021.

”Section 37: What Benefits? Who Benefits? What’s Next?,” Co-presenter with Andrea Skinner, Aird & Berlis LLP Municipal Forum, June 2014.

“Top Ten ‘Legal’ Things a New Councillor Ought to Know [...and an Experienced Councillor Reminded of!]," Co-presenter with Leo Longo, Ontario Small Urban Municipalities Conference, May 2011.

Selected Publications

“The CRA Attacks Municipal Procurement Corruption,” Aird & Berlis LLP Municipal & Planning Law Newsletter, Fall 2011.

"RSJ Holdings v. Inc. London (City): Case Annotation," Co-author with John Mascarin, Municipal & Planning Law Reports (4th), 2008.

"Municipal Decision-Making and the Open Meeting Requirement," Co-author with John Mascarin, The Digest of Municipal & Planning Law (2d), September 2007.


  • LLB, University of Windsor, 2008
  • MPA (Hons.), Local Government, University of Western Ontario, 2002
  • BA (Hons.), Urban and Regional Planning, Ryerson University, 2001