To start with, here are Rothstein and Moldaver JJ. for the majority at para. 42-43, reading the word "irregularity" to require serious corrosion of the electoral process in order to result in results being overturned:
The word “irregularities” appears as part of the following phrase: “irregularities, fraud or corrupt or illegal practices”. These are words that speak to serious misconduct. To interpret “irregularity” as meaning any administrative error would mean reading it without regard to the related words.One can disagree with Wrzesnewskyj's strategic choice not to argue that "fraud, corrupt or illegal practices" formed part of his basis for challenging the results. But the Supreme Court majority pointed to these terms as reflecting "serious misconduct...capable of undermining the integrity of the electoral process" - meaning that today's decision may actually support challenges to electoral outcomes based on Robocon and other concerns about electoral fraud. And Wrzesnewskyj's case failed because his evidence didn't show irregularities meeting that standard.
The common thread between the words “irregularities, fraud or corrupt or illegal practices” is the seriousness of the conduct and its impact on the integrity of the electoral process. Fraud, corruption and illegal practices are serious. Where they occur, the electoral process will be corroded. In associating the word “irregularity” with those words, Parliament must have contemplated mistakes and administrative errors that are serious and capable of undermining the integrity of the electoral process.
Meanwhile, the majority also discussed at para. 44-45 the constitutional importance of allowing citizens to exercise the right to vote:
Central to the issue before us is how willing a court should be to reject a vote because of statutory non-compliance. Although there are safeguards in place to prevent abuse, the Act accepts some uncertainty in the conduct of elections, since in theory, more onerous and accurate methods of identification and record-keeping could be adopted. The balance struck by the Act reflects the fact that our electoral system must balance several interrelated and sometimes conflicting values. Those values include certainty, accuracy, fairness, accessibility, voter anonymity, promptness, finality, legitimacy, efficiency and cost. But the central value is the Charter-protected right to vote.This is where the Cons' defence of Opitz' seat may serve as a pyrrhic victory which ultimately undermines their goal of restricting access to the polls. That is, unless there's enough backlash against the Supreme Court's decision to give them an excuse to impose new ID requirements and other means of limiting participation.
Our system strives to treat candidates and voters fairly, both in the conduct of elections and in the resolution of election failures. As we have discussed, the Act seeks to enfranchise all entitled persons, including those without paper documentation, and to encourage them to come forward to vote on election day, regardless of prior enumeration. The system strives to achieve accessibility for all voters, making special provision for those without identification to vote by vouching. Election officials are unable to determine with absolute accuracy who is entitled to vote. Poll clerks do not take fingerprints to establish identity. A voter can establish Canadian citizenship verbally, by oath. The goal of accessibility can only be achieved if we are prepared to accept some degree of uncertainty that all who voted were entitled to do so.
Which means that the best response to the Supreme Court's decision is to encourage the precedent placing the Charter right to vote at the core of our electoral process, while highlighting the fact that there are still serious questions about real misconduct - not procedural irregularities - being raised in other cases.