A small group of landed immigrants with republican views who have refused Canadian citizenship because the ceremony involves swearing an oath to the Queen will be in a Toronto courtroom on Friday, facing off with the federal government in an attempt to have this citizenship requirement declared unconstitutional.

But with a royal baby on the way, and a federal government under Prime Minister Stephen Harper that has dedicated itself to reviving the country's connection to the monarchy – restoring the word Royal to the Royal Canadian Air Force, among other measures – the dissenters may have their work cut out for them.

In court, the federal government is set to argue simply that immigrants who disagree with the idea of a hereditary head of state, and refuse to swear an oath of loyalty, do not deserve the benefits of citizenship.

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"The inability to enjoy the benefits of citizenship – to hold a Canadian passport and to vote – are amongst the costs reasonably borne by individuals whose personal beliefs run contrary to Canada's foundational constitutional structure," a lawyer for the federal Attorney-General says in written arguments submitted in advance of Friday's hearing.

The Toronto lawyer for the people fighting the oath, Peter Rosenthal, said that position was surprising: "The Attorney-General has taken the position that if you don't believe in the monarchy, it's appropriate to deny you the right to vote. That's pretty extraordinary, given the fact that more than half of Canadians don't believe in the monarchy."

Friday's court fight is the latest chapter in more than 20 years of failed legal challenges to the citizenship oath spearheaded by Trinidadian-born Toronto activist and lawyer Charles Roach, who died last year at 79, never having become a Canadian citizen.

Mr. Roach, a long-time friend of Mr. Rosenthal, refused to swear the oath and become a citizen because he believed the Queen was a symbol of imperialism and because of injustices done to his ancestors in the name of the British monarchy.

Among the would-be citizens now represented by Mr. Rosenthal is Michael McAteer, 79, a long-time republican who grew up in Ireland but has lived in Canada since 1964. He has never been able to become a citizen because of his refusal to swear the oath.

Mr. McAteer, a former journalist at the Toronto Star, calls the monarchy an "anachronistic" institution ill-suited to Canada's multicultural society.

"I obey the law. I've probably seen more of Canada than most Canadians. I've shovelled my sidewalk, and you know, paid taxes," he said. "I feel very comfortable here, in Canada. But still, after all that, I still cannot become a Canadian citizen."

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The legal application in court Friday seeks to have the part of the oath that refers to swearing allegiance to "Queen Elizabeth the Second, Queen of Canada, her Heirs and Successors" struck down because it violates the protections for freedom of religion and conscience in the Charter of Rights and Freedoms.

The applicants also argue it violates their freedom of expression, by appearing to bar them from agitating for the abolishing of the monarchy, although they acknowledge this would probably never be enforced against them. They also argue the oath is discriminatory, because citizens born in the country are not required to swear allegiance to the Queen.

One of the applicants, Simone Topey, is a Rastafarian, who, according to a court filing, believes that the Queen is the "Queen of Babylon" and that swearing the oath would "deeply violate her religious belief." Another applicant, Dror Bar-Natan, calls the oath "repulsive" because he says the Queen is a symbol of inequality.

A spokeswoman for the Ministry of Citizenship and Immigration said the government had no plans to change the oath.

"Canadian citizenship is an honour and a privilege," spokeswoman Sonia Lesage said. "The government has been working hard to maintain the integrity of the system and to increase the value of Canadian citizenship."