Three permanent residents opposed to taking an oath to the Queen as a condition of Canadian citizenship are taking their battle to Ontario's top court today.

They argue the requirement is discriminatory and violates their constitutional rights and should be struck down.

The three oppose the oath on religious or conscientious grounds, saying it should be optional or that pledging allegiance to Canada should be enough.

A lower court judge, however, disagreed, saying any charter violation can be justified in a democratic society.

Ottawa argues the oath has been around for ages, nothing forces permanent residents to become citizens, and nothing precludes them from opposing the monarchy.

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.

Should Canadian citizenship require an oath to the Queen?