The Ontario Court of Appeal has ruled that prohibiting same-sex marriages is against the Canadian Charter of Rights and Freedoms. In the unanimous June 10, 2003 ruling on Halpern et al v Attorney General of Canada et al Ontario's highest court said that the common law definition that marriage be between "one man and one woman" offends the equality rights in the Charter of Rights. The Court declared that definition invalid and provided a new definition of marriage as the "voluntary union for life of two persons to the exclusion of all others." The Court said that the new definition would take effect immediately.

The judgment also ordered the Clerk of the City of Toronto to issue marriage licenses to the seven couples in the case. One of those couples, Michael Leshner and Michael Stark, married shortly after the decision. The marriage has not yet been registered, which can take weeks, but the Ontario Attorney General told reporters that same-sex marriages would be registered.

The Court ordered that the Registrar General of the Province of Ontario also register the marriages of Kevin Bourassa and Joe Varnell and of Elaine and Anne Vautour. The two couples were married in January 2001 in Metropolitan Community Church in Toronto which used the tradition of issuing bans to avoid the need for a city marriage license.

On June 17, 2003 the federal government announced that it would not appeal the decision to the Supreme Court of Canada. Instead it plans to introduce legislation to redefine marriage to include same-sex unions.

Currently in Canada, the federal government is responsible for defining what constitutes a marriage.

Provincial governments are responsible for the administration and procedural requirements of the marriage ceremony and for issuing marriage licenses.