Giselle Mazmanian advises clients on complex environmental regulatory and transactional matters. Her practice encompasses Superfund and RCRA remediation, environmental due diligence, brownfield redevelopment, and regulatory compliance. She also counsels clients on emerging contaminants, including per- and polyfluoroalkyl substances (PFAS), cross-border environmental matters, and environmental, social, and governance (ESG) policies and programs.

Before joining the firm, Giselle practiced environmental and energy law for nearly a decade at a leading Canadian law firm, advising clients across a range of industries on environmental regulatory, transactional, and litigation matters. Her experience practicing in both the United States and Canada provides her with a valuable perspective on the legal and regulatory challenges facing businesses operating across borders.

Prior to her legal career, Giselle worked as an environmental scientist and engineering consultant. Drawing on this multidisciplinary background, she combines legal and technical insight to help clients evaluate environmental risks, navigate complex regulatory requirements, and develop practical strategies for regulatory matters and environmental litigation.

Giselle is admitted to practice in New York and Ontario and is recognized by the Law Society of Ontario as a Certified Specialist in Environmental Law. She has been named a “Lawyer to Watch” in mining and energy law by Lexpert Canada and is a recipient of the Armenian Bar Association’s “20 Under 40 Rising Stars” Award.

Giselle serves as Chair of the Remediation and Chemicals Subcommittee of the New York City Bar Association’s Environmental Law Committee and is an active member of the Environmental Law Network’s Future Leaders’ Division.

In her free time, Giselle enjoys hitting the tennis court, going for a run and playing the piano.

Representative examples of Giselle’s work include:

Transactional

• Representing corporations in acquisitions and divestitures, including conducting due diligence, advising on environmental compliance, and drafting and negotiating protective environmental provisions in agreements.
• Assisting developers and investment companies with pre-purchase due diligence and brownfield redevelopment.
• Representing commercial landlords and tenants in negotiating favorable environmental terms in lease agreements.

Environmental Regulatory Compliance and Remediation

• Establishing audit programs and compliance tools for clients in the steel manufacturing, food processing, waste management, and mass transit industries to identify and address environmental compliance and management system implementation gaps across air, water, and waste media.
• Developing PFAS compliance programs for clients in the aerospace, food and beverage, and textile industries.
• Assisting potentially responsible parties at Superfund and RCRA corrective action sites with liability assessment, remedy selection, and allocation issues.
• Assisting clients in securing air, water, and waste permits, including preparing permit applications, negotiating permit conditions, addressing third-party interests, and appealing permits.
• Advising clients on responses to regulatory demands and environmental obligations associated with contaminated lands, air emissions, stormwater management, sewage works, hazardous waste management, remedial action, and restoration plans.

• Lexpert Canada “Lawyer to Watch” (mining and energy law), 2022. Click here to view selection methodology.
  
  Global Armenian Bar Association’s “20 under 40 Rising Stars” Award, 2022. Click here to view selection methodology.

“Greenbiz and Getting to Market: What It Takes to Go Green and Limit Liability”, American Bar Association Tort Trial and Insurance Practice Section, the Brief, April 25, 2019 – with M. McAree

“A Rights‐Based Approach to Indigenous Women and Gender Inequities in Resource Development in Northern Canada.” Rev Eur Comp Int Environ Law, 2018; 27(1):63-74 – with K. Koutouki and K. Lofts

“Should Citizens Expect Procedural Justice in Nonadversarial Processes? Spotlighting the Regression of the Citizen Submissions Process from NAAEC to CAFTA-DR” in NAFTA and Sustainable Development: History, Experience, and Prospects for Reform (New York: Cambridge University Press, 2015).

"The Eight-Minute Environmental Lawyer 2026 - U.S. PFAS Regulations and Litigation and Potential Impacts for Canada," presented at the Law Society of Ontario CPD Program, September 17, 2026

"Managing Risk and Liability: Legal Issues on Emerging Contaminants," presented virtually as part of SWEP's Emerging Contaminants seminar, August 28, 2025

"Cross-border (U.S./Canada) PFAS Regulatory Overview and Litigation Trends," presented virtually at the Environmental Law Network, Future Leaders Division meeting, March 27, 2025

"Citizen Science and Accountability - A Rare Victory Over an International Plastics Manufacturer in San Antonio Bay Estuarine Waterkeeper v Formosa Plastics Corp.," presented at a SWEP Lunch and Learn webinar, March 28, 2024

“Trends in Environmental Litigation Cross-Border”, presented at the Ontario Bar Association's Ontario Legal Conference: Cross-Border (US/Canada), Toronto, Ontario, May 4, 2023

“Environmental Permitting,” presented at The Osgoode Professional Development Certificate in Mining Law. York University, Toronto, Ontario. Faculty Lecturer since 2022

“Environmental Case Law and Regulatory Update”, presented at the Ontario Bar Association’s Ontario Legal Conference Municipal, Planning & Environmental Law, Toronto, Ontario, February 9, 2023

“Canadian Environmental Law Training Course (2-day intensive)” presented to company engineers, scientists and environmental practitioners, Burlington, Ontario, January 24- 25, 2023

“Air Quality Challenges: Environmental Compliance, Climate Change and COVID-19 Safe Spaces”, presented at CANECT – Environmental Compliance and Due Diligence Training, Vaughan, Ontario, April 28, 2022

“Water & Wastewater Regulation and Compliance 2022: An Interactive Case Study”, presented at CANECT – Environmental Compliance and Due Diligence Training, Vaughan, Ontario, April 27, 2022

“The Rising Impacts of Climate Change and the Law”, a webinar series on emerging and developing areas of law presented by the Armenian Bar Association, June 24, 2021.

“Edibles, Extracts and the Environment – Minimizing the Legal Risks of Cannabis”, presented at the 4th Annual National Conference on Food Law and Policy, University of Toronto, Toronto, Ontario, November 8, 2019

“Statutory Interpretation”, presented as part of the University of Toronto Guest Lecture Environmental Regulations course, University of Toronto, Toronto, Ontario, February 17, 2019