Rocco Galati, fellow lawyer Manuel Azevedo and the Constitutional Rights Centre have filed a notice of application in the Federal Court of Canada arguing Parliament reached beyond its jurisdiction in passing the controversial measures.
They are asking the court to declare the Strengthening Canadian Citizenship Act unconstitutional, citing citizenship protections ranging from the Magna Carta to the Constitution Act, 1867.
For years, a newcomer could be stripped of Canadian citizenship if they attained it through false representations.
The new law, which received royal assent last week, expands the list of those vulnerable to revocation to people born in Canada but eligible to claim citizenship in another country — for instance, through their parents.
It also broadens the grounds for revocation to include several criminal offences including espionage, treason or terrorism.
Opposition MPs have denounced the provisions as arbitrary and nonsensical, as revocation could now result in deportation to a country the person has never set foot in.
The Canadian Bar Association said the new law revives the medieval punishment of banishment.
Galati and his associates are also seeking a court order prohibiting citizenship revocation and removals under the new provisions.
They also want the government to file copies of "any and all" memos, opinions or legal opinions concerning the constitutional authority of the government to enact the legislation.
Immigration Minister Chris Alexander's office did not answer questions Wednesday regarding the law's constitutionality.
However, the minister has vigorously defended the legislation, saying the public thinks it is "absolutely legitimate" to strip dual nationals of their Canadian citizenship if they commit grave offences.
NDP Leader Tom Mulcair said he wasn't surprised at the legal challenge.
"The Conservatives are at war with a court system that keeps turning back their bizarre legislation that fails to respect Canadians' rights," Mulcair said in an interview.
The Canadian Association of Refugee Lawyers has said it will also fight the citizenship measures in the courts.
The legislation violates equality rights under the Constitution by creating separate classes of Canadians, says Lorne Waldman, president of the association of more than 250 lawyers who represent refugees.
The association also argues the proposed revocation procedures lack fairness and that a provision forcing new citizens to swear they intend to reside in Canada — and risk losing their citizenship if they later go abroad — would mean some Canadians have mobility rights while others do not.
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