Derek Moran
Person�s name
2. (1) For all purposes of Ontario law,
(a) a person whose birth is registered in Ontario is entitled to be recognized by the name appearing on the person�s birth certificate or change of name certificate, unless clause (c) applies;
(b) a person whose birth is not registered in Ontario is entitled to be recognized by,
(i) the name appearing on the person�s change of name certificate, if the person�s name has been changed under this Act or a predecessor of it, or
(ii) in all other cases, the name recognized in law in the last place with which the person had a real and substantial connection before residing in Ontario,
unless clause (c) applies; and
(c) a person who adopted a name on marriage before the 1st day of April, 1987 is entitled to be recognized by that name unless the person subsequently changed that name under this Act or a predecessor of it. R.S.O. 1990, c. C.7, s. 2 (1).
Saving
(2) Nothing in this Act shall be deemed to affect a change of name effected under a right that existed at law before the 26th day of June, 1939. R.S.O. 1990, c. C.7, s. 2 (2).
Surname and forename
(3) A person�s name may not be changed under this Act so as to include no surname or so as to include no forename. R.S.O. 1990, c. C.7, s. 2 (3).
http://www.e-laws.gov.on.ca/html/statutes/english/elaws_statutes_90c07_e.htm