The Supreme Court of Canada recently upheld the Ontario Court of Appeal’s interpretation of the statutory term “material change” in the decision Lundin Mining Corp. v. Markowich 2025 SCC 39. The issue before the court was whether a lower court had applied an overly restrictive definition of material change under the Ontario Securities Act when considering a leave application for a securities class action. Both the Ontario Court of Appeal and the Supreme Court found that the initial motions judge imposed an unduly narrow interpretation of “material change” and that the statutory terms should be given a flexible and contextual meaning within the statutory framework. The Supreme Court confirmed that determining material change involves a two-step test: first, whether there has been a change and second, whether that change is material in all the circumstances. The decision emphasizes that courts should interpret terms like “change”, “business”, “operations” and “capital” with reference to the purpose of the statutory regime and the context in which they arise rather than through rigid definitions.
Although Lundin Mining Corp. is a securities law case, the underlying legal principle — that courts must consider the context and significance of a change — resonates with how family courts in Ontario approach material change in circumstances in family law applications.
In family law, a material change in circumstances is the legal threshold a party must meet to vary a final order. For example, to change custody, parenting time, decision-making responsibility, child support or spousal support, a party typically must demonstrate that circumstances have changed significantly since the last order was made. Under the Divorce Act and related family legislation, this ensures that variations address genuine and substantial changes rather than routine disagreements or issues that were foreseeable at the time of the original order.
Family law jurisprudence has long established that a material change must be significant, enduring and unforeseeable in relation to the circumstances at the time the original order was made. The Supreme Court of Canada in earlier family law cases described this concept as requiring evidence that conditions, means, needs or other circumstances have changed in a way that materially affects the parties or the children involved. Changes that were already contemplated when the original order was made, or those that are minor or temporary, will not typically meet the threshold.
The policy rationale in family law is clear. Final orders and separation agreements are intended to provide certainty and stability. The material change threshold prevents endless attempts to rewrite orders based on predictable developments or differences of opinion about how an order is working in practice. Only when circumstances have genuinely shifted and that shift has practical consequences should a court consider altering existing arrangements.
For legal practitioners and clients in Ontario family law matters, the Supreme Court’s recent commentary in Lundin Mining Corp. underscores the broader judicial preference for contextual interpretation of statutory concepts. In family law, this means that proofs of material change must be grounded in the realities of the parties’ lives and supported by evidence showing why the previously-ordered arrangements are no longer appropriate. It also reinforces that judges have discretion to assess the significance of changes in light of the original order’s terms and the specific factual context.
Understanding how courts define and apply “material change” is vital for any family law practice area where variation of orders is a possibility. Legal advice early in the process, thoughtful preparation of evidence, and a clear articulation of why circumstances have meaningfully changed remain essential to success on a motion to vary a final order.
