Karen Ensslen

Lawyer, she/her/hers


Committed to the interests of unions, associations, workers and pensioners, Karen Ensslen is a litigator with strong strategic thinking skills and a passion for resolving complex multi-party disputes.

Karen’s ability to formulate effective plans for action and deliver results meaningful to clients lies at the heart of her strength as a lawyer. Focusing on all aspects of labour and employment law, as well as on human rights and constitutional law, she advocates for clients in labour arbitration, human rights, professional discipline and other administrative proceedings, and before all levels of court in Ontario and at the Supreme Court of Canada.  Karen has particular expertise representing employees and pensioners in employer insolvency proceedings.

Karen’s achievements range from a high-profile defense of the pension rights of retired steel workers imperilled by the restructuring of an insolvent employer to a successful appeal of an arbitration panel’s finding against a long-time employee whose employer failed to enrol him in a mandatory pension plan. She has played a prominent role in convincing the courts to strike down legislation imposing collective agreements on education workers, defending Occupy Toronto against eviction notices from the City of Toronto and defending employees’ privacy rights against unreasonable drug- and alcohol-testing policies before the Supreme Court of Canada. Karen brings passion, intelligence and determination to her client’s problems, whatever the task.

Karen has published on issues such as disability accommodation, privacy rights, drug-testing limits and sex education curricula in a variety of places including the Education Law Journal, Education Forum and the Ontario Bar Association. In law school, she was co-editor-in-chief of the Journal of Law and Equality. She has been a program chair, moderator and featured speaker for the Ontario Bar Association (OBA), the Canadian Association of Labour Lawyers (CALL), and Lancaster House.

Karen studied law at the University of Toronto and holds a B.A. cum laude in economics and history from Columbia University. 

Decisions of Interest

Ontario English Catholic Teachers Assoc. v. His Majesty, 2022 ONSC 6658

  • A freedom of association case in which, as co-counsel, Karen worked in coalition with a large number of other unions to strike down this legislation and affirm the fundamental right of workers to set their own priorities, to bargain collectively and to strike. 

Pay Equity Negotiation

  • Karen negotiated a pay equity plan for 25,000 hospital professionals across over 50 hospitals in Ontario, rectifying systemic gender discrimination in compensation over a 15-year period. This multi-million dollar agreement provides pay equity adjustments to workers in female-dominated job classes into the future.

Ernst & Young Inc. v. Essar Global Fund Ltd. et al, 2017 ONSC 1366

  • An oppression remedy case in which Karen successfully argued that the interests of retired and former members of the Essar Steel Algoma Inc. pension plans had been unfairly disregarded by the company’s parent corporation in certain financial restructuring transactions. 

OPSEU v Ontario, 2016 ONSC 2197

  • A freedom of association rights case in which, as co-counsel, Karen helped persuade the court to strike down legislation imposing collective agreements on all education-sector workers.

Canadian Artists’ Representation v. National Gallery of Canada, 2014 SCC 42

  • A labour rights case in which, as co-counsel, Karen helped persuade the Supreme Court of Canada to find that the National Gallery of Canada bargained in bad faith with the Canadian Artists’ Representation and to uphold the rights of artists to bargain the use of copyrighted works collectively.