In that case, yes he should just be worried about criminality. Marriage fraud is a criminal case also in Canada. See here: http://laws-lois.justice.gc.ca/eng/acts/I-2.5/FullText.html
Misrepresentation
127 No person shall knowingly
(a) directly or indirectly misrepresent or withhold material facts relating to a relevant matter that induces or could induce an error in the administration of this Act;
(b) communicate, directly or indirectly, by any means, false or misleading information or declarations with intent to induce or deter immigration to Canada; or
(c) refuse to be sworn or to affirm or declare, as the case may be, or to answer a question put to the person at an examination or at a proceeding held under this Act.
128 A person who contravenes a provision of section 126 or 127 is guilty of an offence and liable
(a) on conviction on indictment, to a fine of not more than $100,000 or to imprisonment for a term of not more than five years, or to both; or