The courts could still overturn Quebec’s secularism bill even though it includes a provision to invoke the notwithstanding clause to shield it from judicial challenges, legal scholars say.

One possible argument would be that the proposed law, Bill 21, would mainly affect women, a form of sexual discrimination that the notwithstanding clause cannot override.

Another ground for challenge is a past Supreme Court ruling in which a plurality of judges held that religious freedom was outside the scope of provincial jurisdiction.

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Bill 21 would prohibit judges, police officers, teachers and other public workers in positions of authority from wearing visible religious items. The draft legislation also would require that people provide or receive services with faces uncovered when necessary for security or identification reasons.

The bill invokes Section 33 of the Canadian Charter of Rights and Freedoms, which enables governments to override some parts of the Charter for up to five years. Quebec Premier François Legault released a video on Sunday saying that using the clause would prevent “long judicial battles ... it’s a legitimate tool.”

Kerri Froc, a University of New Brunswick law professor, noted that the bill’s history shows it is mainly aimed at women who wear the hijab or the niqab.

“Just because a certain group of women are targeted rather than all women doesn’t make it any less a sex-based distinction,” Prof. Froc said in an e-mail interview.

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Muslim women would also be more affected than Muslim men, because the bill would not prohibit beards. (Quebec Immigration Minister Simon Jolin-Barrette told reporters that tattoos or Rastafarian dreadlocks wouldn’t be banned because the bill applies only to “something that is not naturally on you.”)

If it can be argued that the bill would discriminate against women, Prof. Froc said, then it would contravene Section 28 of the charter, which guarantees gender equality “notwithstanding anything else in this charter.”

Prof. Froc said this means Section 28 cannot be circumvented by Section 33, the notwithstanding clause.

She pointed to Syndicat de la fonction publique v. Quebec, a 2004 Quebec Superior Court decision by Justice Carole Julien, who reviewed various legal interpretations and found that “the prevailing opinion leans towards Section 28 superseding Section 33.”

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Similarly, a 1984 Nova Scotia ruling, Boudreau v. Lynch, said of Section 28 that “the legislators have treated sexual discrimination as the most odious form of discrimination and taken away from legislative bodies the right to perpetrate it in the future.”

Mr. Jolin-Barrette’s special adviser on the file is University of Sherbrooke law professor Guillaume Rousseau, a supporter of the use of override clauses.

“Despite its poor reputation in some circles, this provision is a powerful tool at the service of Quebec identity, social progress and democracy,” Prof. Rousseau wrote in a March, 2016, study.

The study argued that the use of override clauses such as Section 33 is not uncommon in Quebec and can be a legitimate option.

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However, another University of Sherbrooke law professor, Maxime St-Hilaire, said that in many of those cases, Quebec didn’t need to invoke an override clause because the Charter was not a threat.

And the frequency with which override clauses have been invoked doesn’t make the use of Section 33 more appropriate, Prof. St-Hilaire said in an e-mail.

He said the override clause might not protect Bill 21 because the province doesn’t have jurisdiction on religious freedom.

He pointed to Saumur v. Quebec, a Supreme Court decision from 1953.

Laurier Saumur had been arrested for handing out Jehovah’s Witness literature. He challenged a city of Quebec bylaw that outlawed the distribution of any tracts without permission from the police.

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In ruling in Mr. Saumur’s favour, four of the nine judges took the position that religious freedom was federal jurisdiction, two raised the same point without endorsing it and three thought it could be within the scope of the province.

Prof. St-Hilaire noted that the charter explicitly states: “Nothing in this charter extends the legislative powers of any body or authority.”