Section 3 of the Charter broadly guarantees every citizen’s right to vote, a fundamental right that cannot be overridden under s. 33. The Court interprets it purposively as ensuring a meaningful opportunity to participate in choosing elected representatives. The Canada Elections Act gives effect to that right and must be read consistently with its purpose of enfranchising entitled voters and enabling their democratic choices. In construing s. 524(1)(b), the right to vote and that enfranchising purpose are central. They must nevertheless be reconciled with procedural safeguards that ensure only entitled persons vote and preserve electoral integrity and public confidence.

In Opitz, the majority interpreted “irregularities” in light of its neighbouring terms, “fraud or corrupt or illegal practices,” under the associated-words rule. Their common feature is serious conduct capable of affecting electoral integrity. Parliament therefore contemplated serious administrative mistakes, but not every error or deviation from statutory procedure qualifies. Non-compliance with legislation, standing alone, is insufficient to justify annulling an election.

Opitz requires “irregularities” to be understood against competing democratic values, including the right to vote, accuracy, fairness, accessibility, finality, legitimacy, efficiency and cost. Because elections are administered by thousands of workers in difficult conditions, some imperfection is inevitable; the system seeks to enfranchise entitled voters as fully as possible, not perfection. The election-contest process must balance restoring reliable results against prompt finality and electoral stability. Annulment is therefore reserved for cases where an irregularity is proven to have affected the result and undermined electoral integrity.

Opitz adopted a substantive rather than procedural approach to s. 524(1)(b). A procedural breach does not automatically invalidate a vote; safeguards serve the underlying right to vote and are not ends in themselves. The applicant must prove each part of a three-step test on a balance of probabilities. First, there must be an irregularity: a serious administrative error capable of undermining the electoral process and directly bearing on a person’s right to vote. Second, it must have affected the result by allowing an ineligible person to vote or improperly preventing an entitled person from voting. Third, the court retains discretion under s. 531(2) to annul, guided by whether the votes cast doubt on the winner or the irregularity calls electoral integrity into question. Ballot secrecy prevents examining voters’ actual choices.

This is a statutory appeal under s. 532, so appellate rather than judicial-review standards apply. Questions of law are reviewed for correctness; factual and mixed findings require a palpable and overriding error unless an extricable legal error is present. Discretionary decisions receive deference unless affected by legal error, a material factual misapprehension, or a failure to exercise discretion judicially. Jamal J. concludes that the Superior Court made errors of law at each stage of the Opitz framework, warranting intervention.

An irregularity under s. 524(1)(b) need not involve breach of legislation. Opitz includes both breaches of provisions establishing entitlement to vote and serious administrative errors capable of undermining electoral integrity by directly affecting an individual’s right to vote. The Superior Court therefore erred in treating intentional, dishonest or bad-faith conduct as necessary. Opitz itself treated clerical mistakes as irregularities even without fraud or corruption. Although no specific statutory provision governed the mail-in procedure, the known postal-code mistake and Elections Canada’s failure to correct it for more than three weeks constituted a serious administrative error. Elections Canada had contact information for about 40 affected electors, could have arranged alternatives, and was expected to report the error. Its inaction prevented at least one vote from being counted.

The second Opitz step concerns whether the irregularity changed the vote count, not whether it can be shown to have changed the electoral outcome through the voter’s preference. Bossé’s ballot was not delivered or counted because of the postal-code error and Elections Canada’s failure to remedy it, establishing the required causal link. The Superior Court erred by considering that Bossé voted for Sinclair-Desgagné, since ballot secrecy precludes investigating voters’ choices at any stage. Sections 239(2) and 240 place responsibility on electors for external contingencies, such as postal delays or late mailing, but do not relieve Elections Canada of errors within its control. Bossé followed the prescribed process and mailed her ballot 22 days before polling day; she was not required to verify official materials or correct Elections Canada’s mistake.

Under s. 531(2), annulment is discretionary, guided by whether the affected votes cast doubt on the winner and whether the irregularities undermine electoral integrity. The Opitz “magic number” test requires annulment where affected votes equal or exceed the victory margin; that test is met because one ballot was lost in an election won by one vote. The Superior Court erred in relying on three unresolved recount objections, which could not be revisited indirectly after the certified recount; on Bossé’s ability to track her ballot; and on alternative voting methods. Those considerations could not transfer responsibility for Elections Canada’s known, correctable error to the elector or make the contested-election regime unavailable whenever in-person voting remained possible. Although annulment is a serious remedy, the magic-number result left no discretion not to annul. The Terrebonne election must therefore be annulled.

The ruling does not expose elections to challenges over every mistake. The relevant irregularity is narrowly defined: a serious Elections Canada error affecting an elector’s franchise, discovered in time to correct, recognized as requiring correction, but left uncorrected. Minor errors, promptly corrected errors, and errors not affecting the right to vote remain outside the approach. Applicants must still prove on a balance of probabilities that the irregularity affected the result, and courts retain residual discretion not to annul. The present combination—a confirmed lost ballot and a one-vote margin—is extremely rare.

The Superior Court made no order for costs because the application raised issues of public importance and it would be unfair to make Sinclair-Desgagné pay. Jamal J. adopts the same approach in the Supreme Court, particularly because none of the candidates caused the error giving rise to the proceedings. No costs should be awarded in either court.

The Canada Elections Act seeks both to enfranchise eligible voters and to protect the integrity of the democratic process. It implements s. 3 of the Charter, whose positive and collective dimensions require meaningful participation, effective representation and electoral machinery capable of recording and implementing the people’s will. The Act balances values including accuracy, fairness, accessibility, legitimacy, efficiency and finality. Accordingly, s. 524(1)(b) cannot demand perfect certainty: protecting one person’s vote may conflict with the rights of all other electors. Courts must therefore interpret the provision with regard to the integrity of the electoral system as a whole.

Under Opitz, an election challenge proceeds in three distinct steps: proving an irregularity, fraud, corruption or illegality; proving that it affected the result; and, if both thresholds are met, deciding whether to annul the election. The issue here is whether incorrect postal codes on some special-ballot envelopes constitute an irregularity. Opitz identifies two categories: breaches of statutory procedures, and administrative errors that are both serious and capable of undermining electoral integrity. The first step concerns the nature and systemic impact of the conduct, not merely an individual’s right to vote; the latter is addressed at the second step. Simple, honest, isolated clerical errors do not meet the required gravity, which must be comparable to fraud, corruption or illegality. The impact inquiry asks whether public confidence in the legitimacy and finality of elections is undermined. A high threshold is necessary because elections involve extensive nationwide administration, and an unduly low one could disrupt results and disenfranchise many voters.

The error was a minor, unintentional clerical mistake: the envelope had the correct recipient, street address, city, province and first three postal-code characters, with only the final three characters entered incorrectly. Although the worker failed to notify his supervisor or take further corrective measures, that omission did not elevate the mistake to conduct comparable to fraud, corruption or illegality. Mail-in voting’s risks are known and addressed through statutory safeguards, including the elector’s responsibility to ensure receipt. The affected voter could have used the tracking number and voted in person, but did neither. In the authors’ view, it would be inconsistent for the Act to assign that responsibility to the elector while permitting an election to be annulled for this kind of error.

An error affecting one vote was not capable of undermining electoral integrity. Elections Canada reported in 2013 that administrative rules were not followed in 1.3 percent of voting transactions, illustrating that some human error is inevitable. Mail-in voting adds procedural risks but provides tracking numbers and notices so electors can verify delivery, while ss. 239(2) and 240(b) place responsibility for receipt on them. This isolated error therefore could not undermine public confidence in the legitimacy and finality of elections, and the threshold for reopening the election was not met.