Hmmm, looks like there is a legal method to remove citizenship from immigrants.
From the Citizenship Act.
"10. (1) Subject to section 18 but notwithstanding any other section of this Act, where the Governor in Council, on a report from the Minister, is satisfied that any person has obtained, retained, renounced or resumed citizenship under this Act by false representation or fraud or by knowingly concealing material circumstances,
(a) the person ceases to be a citizen, or
(b) the renunciation of citizenship by the person shall be deemed to have had no effect,
as of such date as may be fixed by order of the Governor in Council with respect thereto.
Presumption
(2) A person shall be deemed to have obtained citizenship by false representation or fraud or by knowingly concealing material circumstances if the person was lawfully admitted to Canada for permanent residence by false representation or fraud or by knowingly concealing material circumstances and, because of that admission, the person subsequently obtained citizenship.
1974-75-76, c. 108, s. 9."
http://laws.justice.gc.ca/en/C-29/33703.html#rid-33737Note that the Governor in Council is the Governor General wearing a different hat.