Allowing would-be citizens to opt out of a "repugnant" oath to the Queen would cause no harm and allow them to retain their sense of integrity, Ontario's top court heard Tuesday.

In calling for the citizenship oath to be struck down, a trio of longtime permanent residents argued the requirement is discriminatory and violates their religious and conscientious beliefs.

"Someone who wants to be a citizen is being forced to say, 'I support the constitutional monarchy,' their lawyer Peter Rosenthal told the Court of Appeal.

"How repugnant must that be to someone who's a staunch anti-monarchist?"

At issue is part of the citizenship oath in which newcomers must promise to be "faithful and bear true allegiance to Queen Elizabeth the Second, Queen of Canada, her heirs and successors."

The trio — Israeli, Irish and Jamaican citizens — say they would be happy to take an oath to Canada, but not to the Queen, who they call a relic that represents privilege and lack of equality.

For its part, the government argues citizenship is voluntary and the three are misinterpreting the oath.

Crown lawyer Kristina Dragaitis said the Queen is at the "apex of the Constitution" and symbolizes the rule of law.

"The Queen and the Constitution protect their rights to dissent," Dragaitis said.

The appellants, she said, are taking a "literal" approach to the oath.

Dragaitis said the government was not conceding the oath infringes on religious beliefs, or that requiring people to take it violates their freedom of expression.

Rosenthal, who pointed to polls showing most Canadians oppose the monarchy, insisted that forcing newcomers to pledge allegiance to the Queen could make them hypocrites and discourage them from anti-monarchist causes.

The three justices hearing the case frequently challenged both lawyers.

Justice Peter Lauwers said the appellants seemed to have an "unsophisticated" view of the oath in maintaining it speaks to their integrity.

"We have different notions of integrity," Rosenthal said.

"That's not appropriate," Lauwers responded.

Simone Topey, 47, a Rastafarian, maintains her religion forbids taking an oath to the Queen.

"Some people might object to taking any oaths at all on religious grounds," Lauwers said. "Do we do away with all oaths?"

Rosenthal said it would depend on the circumstances.

Michael McAteer, 80, a staunch republican from Ireland, says the oath is unnecessary and would violate his conscience, while Dror Bar-Natan, 48, an Israeli, said the Queen represents entrenched privilege he opposes.

Dragaitis said it would be very difficult trying to sort out what constitutes a conscientious objection to the oath.

Native-born Canadians do not have to take any oath, hence the argument that permanent residents are discriminated against on the basis of nationality or origin.

Australia, also a constitutional monarchy like Canada, did away with its pledge to the Queen 20 years ago, the court heard.

Last September, a lower court judge ruled that any charter violation the oath requirement causes can be justified in a democratic society, prompting the appeal.

The justices reserved their decision.

The government has already made it clear it will take the case to the Supreme Court of Canada if it loses before the Ontario Court of Appeal.