Executive Summary: Key Legal and Evidentiary Issues

• Thanh Quy Mac, a defendant in a defamation action, sought to appeal a decision that dismissed the claim against him but allowed it to continue against unnamed Doe Defendants.

• Standing to appeal was the central issue, as the Court of Appeal found Mac lacked the statutory right to challenge a decision that was ultimately in his favour.

• A party cannot appeal a decision made in their favour, even if they did not obtain all the relief they sought in the proceeding below.

• No direct personal, legal interest was established by Mac in the ongoing litigation against the Doe Defendants, despite his claim that he might be involved as a witness.

• Discretionary non-party standing was denied after the Court applied the five-factor test from Société des Acadiens, finding that none of the factors weighed in Mac's favour.

• The appeal was dismissed, leaving the defamation action against the Doe Defendants intact while confirming the dismissal of the claim against Mac.

The underlying disputes between Dixon and Mac

The case of Dixon v Mac, 2026 ABCA 145, arose from a series of related proceedings in Alberta. Thanh Quy Mac had commenced a personal injury action. James L. Dixon — a lawyer operating through James L. Dixon Professional Corporation (referred to in the singular as "the respondent" by the Court) — subsequently launched a separate suit to collect a legal bill from Mac in relation to that personal injury action. During the course of that legal bill action, Dixon delivered interrogatories to Mac, asking him, among other things, about the nature of their interactions and whether Mac doubted that Dixon and his firm had done the work it billed him for. Mac provided an affidavit responding to the interrogatories.

The defamation claim and the Doe Defendants

Dixon viewed some of the statements Mac made in his affidavit as defamatory and commenced the present action. The pleadings alleged that Mac defamed Dixon in his affidavit in the legal bill action, and that two unnamed parties — referred to as John Doe and Jane Doe (the Doe Defendants) — also defamed Dixon to Mac. The defamation action therefore named Mac as a defendant alongside the two Doe Defendants.

The initial application and the chambers judge's decision

Mac brought an application to have the present action dismissed in its entirety. The application was granted at first instance. Dixon appealed and was partially successful. The dismissal was upheld against Mac, but the action was allowed to continue against the Doe Defendants only. The resulting order was made by Justice G.D. Marriott, dated June 17, 2025, and filed on July 16, 2025.

Mac's appeal to the Court of Appeal of Alberta

Dissatisfied that the action continued against the Doe Defendants, Mac appealed to the Court of Appeal of Alberta, arguing the action should be dismissed in its entirety. He advanced several grounds, including that the chambers judge erred in failing to recognize that the claims against the Doe Defendants should be dismissed by operation of law, that she failed to engage in a truly de novo analysis of the initial decision, and that she applied an improper standard with respect to what constitutes an "extinguished" claim.

The standing analysis

The Court of Appeal — composed of Justices Michelle Crighton, April Grosse, and Joshua B. Hawkes — found it unnecessary to address those issues. Instead, the Court determined that Mac did not have standing to bring the appeal. The Court emphasized that an appeal is a statutory right, and that a party must have statutory authorization to appeal. While the Alberta Rules of Court do not expressly stipulate who is a party for the purpose of filing an appeal, the Court has previously held that the Rules imply that the parties to the proceeding at issue on appeal have a right to appeal, and that, as a general rule, a non-party cannot appeal a decision. The Court further noted the established principle that a party to the proceeding below can only appeal a decision against their interests and cannot appeal a decision in their favour. Although Mac did not obtain all the relief he sought in the proceeding below, he unequivocally was successful — he sought to have the action against him dismissed, and it was. He had no right of appeal from that. Mac's claim that the continuation of the litigation against the Doe Defendants may involve him as a witness was found not to be a sufficient connection to establish a direct personal, legal interest.

Application of the discretionary factors

The Court also considered whether it should exercise its discretion to grant Mac non-party status to appeal, applying the five-factor framework from Société des Acadiens du Nouveau-Brunswick Inc v Association of Parents. Mac's interests were represented in the court below — and successfully, as the action against him was dismissed. He did not have an interest in the litigation against the Doe Defendants that merited protection. To say he was "bound" by the decision was no more than to recognize that he was no longer a party to the action and did not require anything further of him. The Court refrained from commenting on the strengths of Mac's argument that the action should have been dismissed against all parties, so as not to prejudice what remains of the litigation after the order below. Finally, the interests of justice in avoiding a multiplicity of proceedings would not be served by granting Mac status to challenge the decision in respect of the Doe Defendants.

The ruling and outcome

The Court of Appeal dismissed Mac's appeal, holding that the action was dismissed against him and, without any ongoing direct personal interest affected by the order after its pronouncement, he had no standing to bring the appeal. Dixon, as the respondent, was the successful party. No monetary award was determined or granted in this decision, as the appeal was resolved entirely on the procedural question of standing. The memorandum was filed at Calgary, Alberta, on May 4, 2026. Rule 9.4(2)(c) was invoked, and the Court indicated it would prepare the resulting order or judgment.