The Federal government says it now has the power to revoke the citizenship of some Canadians convicted of terrorism, treason or espionage.

A controversial new law, first introduced last June, went into effect on Friday.

The Ministry of Citizenship and Immigration says there are several serious crimes that could result in dual citizens losing their Canadian status.

The ministry says it would revoke citizenship for anyone found guilty of terrorism, treason and high treason, and spying for a foreign government.

The rules would also apply to dual citizens who take up arms against Canada by fighting in a foreign army or joining an international terrorist organization.

The new law has met with strong public criticism, and two Ontario lawyers have already launched a court case arguing it is unconstitutional.

Immigration Minister Chris Alexander argued the new rules are meant to confront what he described as the “ever-evolving threat of jihadi terrorism.”