Maha Kassef, 35, an ambitious elementary schoolteacher, aspires to become a principal. But since she wears a Muslim head scarf, she may have to derail her dreams: A proposed bill in Quebec would bar public school principals, and other public employees, from wearing religious symbols.

“How am I supposed to teach about respect, tolerance and diversity to my students, many of whom are immigrant kids, when the government is asking me to give up who I am?” asked Ms. Kassef, the child of Kuwaiti immigrant parents who worked tirelessly to send her and her four siblings to college.

“What right does the Quebec government have to stop my career?” she added.

Religious minorities in Quebec are reeling after the right-leaning government of François Legault proposed the law last week. It would prohibit not just teachers, but other public sector workers in positions of authority, including lawyers and police officers, from wearing religious symbols while working.

Current public sector workers would get an exemption, though only as long as they stay in the same position within the same organization, according to the bill. This means that a teacher, for example, could not change schools or be promoted if she refused to take off her head scarf.

Mr. Legault, the Quebec premier, has said that the proposed law — which has echoes of legislation in France — is necessary to uphold the separation between the state and religion.

But some municipalities, mayors and education authorities in Montreal, a multicultural city with a large, visible minority community, are in rebellion. Several bodies have vowed to refuse to enforce the measure if, as is expected, it passes.

At a time when the Royal Canadian Mounted Police and cities like New York and London have allowed police officers to wear some forms of religious garb so that they better reflect the communities they serve, some municipal officials, including Montreal’s mayor, Valérie Plante, argued that the law would hamper — rather than improve, as its proponents argue — the integration of minorities.

Beny Masella, the mayor of the suburb of Montreal West, who represents an association of 15 mayors, said he and the other mayors would take issue with being asked to refuse to hire police officers or town clerks because they wore conspicuous religious symbols. He said he would ignore such an interdiction.

“A smart young Sikh with a turban comes into my office and I am supposed to tell him we can’t hire him as a policeman because of his turban?” Mr. Masella asked. “We may lose out on competent employees because of this. This is also a matter of conscience.”

The English Montreal School Board, which administers English-speaking public schools in the city, said it would also defy the bill. “A religious symbol worn by a teacher in no way affects their ability to provide quality education in a secular state,” it wrote in a resolution.

Some head scarf-wearing student teachers at Quebec universities have expressed despair that the law will halt their careers before they have even begun. Some students at the University of Montreal have begun wearing blue felt triangles to show solidarity.

As he defended the proposed law, Mr. Legault, the Quebec premier, posted a video over the weekend on his Facebook page in which he said the legislation respected “our history, our values” and was “an approach that a great majority of Quebecers want.”

“Some will say we’re going too far, others will say we are not going far enough,” he said, adding, “In Quebec, this is how we live.”

Mr. Legault’s approach has come under additional criticism from human rights advocates because in order to fend off legal challenges, he has invoked a rarely used constitutional provision known as the “notwithstanding clause.”

That clause, made part of the Canadian Constitution in 1982, enables Canadian legislatures to override basic constitutional rights like freedom of religion and expression to maintain their independence.

Gregory Bordan, a leading constitutional lawyer, has worn his skullcap to the office for the past 33 years. Soon, he may have to leave it at home if he wants to work for the government or represent his law firm on a government contract.CreditChristinne Muschi for The New York Times

Mr. Legault argues that Quebecers will remain free to practice their religions, and that the “notwithstanding clause” is “a legitimate tool.”

Still, Irwin Cotler, a leading international human rights lawyer in Montreal who was Canada’s justice minister and attorney general, called the proposed law a “broad-based assault on liberal values, including the freedom of religion.”

He said that by invoking the notwithstanding clause to try to insulate the law from legal challenges, the government was displaying disrespect for the fundamental role of the courts in safeguarding constitutionally guaranteed minority rights.

He said opponents of the proposed legislation could potentially seek recourse by filing a complaint at the United Nations Human Rights Committee on the grounds that the bill undermined the 1976 International Covenant on Civil and Political Rights. While the United Nations committee cannot revoke the legislation, its decisions carry moral and legal weight, he said.

Gregory Bordan, a leading constitutional lawyer and a religious Jew, has worn his skullcap to the office for the past 33 years. Soon, he, too, may have to leave it at home if he wants to work for the government or represent his law firm on a government contract.

He said the scope of the proposed bill was far wider than many realized and amounted to a political project to marginalize minorities from the judiciary, education and law enforcement.

Under the proposed legislation, he noted, lawyers who wear a head scarf, cross, skullcap or turban could no longer be retained as external counsel by the government to represent it before the courts or with a third party.

Moreover, a lawyer wearing religious garb could not be hired as an employee of the government, the national assembly or various other public bodies, even if appearing before the courts or a third party was not part of their job description.

“The message that this law sends is that unless you look like us, you can’t participate in public life,” said Mr. Bordan, who represents Coalition Inclusion Quebec, a group of religious minorities.

Mr. Bordan, whose great-grandparents came from Ukraine and Poland to Canada in the early 1900s, added that his parents had insisted he become fluent in French, and that he had been raised as a proud Quebecer. Now he felt betrayed.

“It is an insult to be told I am incapable of being impartial unless I remove my kipa,” he said, referring to his skullcap in Hebrew. “I did everything to become part of the society, and now I am being told that it’s all a sham.”

Public expressions of Muslim identity have been an explosive issue in several European countries, and some defenders of secularism have criticized Muslim head coverings as undermining female empowerment.

Similarly, some proponents of the ban in Quebec have sought to frame it as a form of feminist liberation for Muslim women. The preamble to the bill notes that Quebec “attaches importance to the equality of women and men.”

But Quebec’s women’s federation accused the government of “secularizing the oppression of women.” It said the law would ghettoize Muslim women by excluding them from professional and social life.

Ms. Kassef, the teacher and aspiring principal, noted that if she was forced to teach without a head scarf, it would undermine her ability to be an effective teacher.

“A teacher has to lead by example,” she said, “and can’t give 100 percent if they feel broken, battered and oppressed.”