[2][3][4] It stands today as a landmark Supreme Court case which established that sexual orientation constitutes a prohibited basis of discrimination under section 15 of the Canadian Charter of Rights and Freedoms.

Joseph J. Arvay, Q.C., represented the plaintiffs, who delivered a motion for a declaration of unconstitutionality to the Federal Court of Canada (Trial Division).

Nesbit and Egan asked the Court to remedy the alleged Charter violation by reading the definition of spouse so as to include same-sex couples.

Robertson held the issue in the case was not solely concerned over the question of who may receive spousal allowances, but was in actuality "an indirect challenge to the common law and statutory concept of marriage".

In a concurring judgment, Mahoney JA adopted the reasoning of the trial judge, holding the definition of "spouse" in the Old Age Security Act did not discriminate against the appellants.

Mahoney JA held the Charter challenge was misplaced: in his view, the discrimination the appellants alleged was due to "the failure of the definition to comprehend the concept of common law marriage between persons of the same sex" and not on the basis of their sexual orientation.

In a 4–1–4 vote, the Supreme Court of Canada dismissed the appeal and upheld the constitutionality of the impugned definition of "spouse" in the Old Age Security Act.

La Forest J added in obiter that had he found the impugned definition discriminatory, he would have upheld it under section 1 of the Charter "for the considerations set forth in my reasons in McKinney, supra, especially at pp.

The remaining four justices dissented, all rejecting the "irrelevance" approach as articulated by La Forest J and the "incremental" doctrine suggested by Sopinka J.

The words "of the opposite sex" in the definition of "spouse" specifically exclude homosexual couples from claiming a spousal allowance.

[13] He noted the Court's decision in McKinney was far more complex, having the potential to affect "the entire composition of the workforce; the ability of younger people to secure jobs; access to university resources; promotion of academic freedom, excellence and renewal; collective bargaining rights; and the structure of pension plans".

She contends that the approach defeats the very purpose of the equality rights in Section 15 of the Charter, noting that the objective of the Act in question may be discriminatory per se, but would survive constitutional scrutiny.

Regarding the status of the appellants, she agrees with Cory that they are clearly part of a "highly socially vulnerable group, in that they have suffered considerable historical disadvantage, stereotyping, marginalization and stigmatization within Canadian society.

"[17] As for the nature of the interest affected, L'Heureux-Dubé asserts that the appellants have been "directly and completely excluded, as a couple, from any entitlement to a basic shared standard of living for elderly persons cohabiting in a relationship analogous to marriage."

The message this denial gives, L'Heureux-Dubé argues, seems undeniable: She finds, therefore, that the exclusion of same-sex couples is indeed discriminatory and in violation of Section 15 of the Charter.

The difficulty in determining the ratio decidendi that Egan established is illustrated by the case Re Rosenberg et al. v. Attorney General of Canada.

Counsel for the Attorney General of Canada conceded that the definition of "spouse" in the Income Tax Act, in light of Egan, violated Section 15 of the Charter.

Nonetheless, they contended that since Egan could not be distinguished from the case at hand, the violation must be upheld under Section 1 of the Charter as matter of stare decisis.

Confusion surrounding the conflicting approaches laid out in Egan has subsided with the formulation of a new Section 15 analysis established by a unanimous Supreme Court in Law v. Canada (Minister of Employment and Immigration).