>>Is there a law against it here in Canada? If so, I've never heard about it.
>
>That, I wouldn't be able to tell. What I know is that I never heard anything about it here.

I got this from the Government of Ontario Web Site. I suspect the lack of gender specificity in the wording is deliberate, and that either spouse can change his/her surname to the spouse's. I certainly can't see why there would be a law preventing it.

Change of Name 
 
Electing to change your name to a partner´s or spouse´s name

Individuals may choose to change their surname (family name) or a combination (hyphenated 
surname) as a result of marriage or a relationship by filling out an Election Change of Name 
form. 

Couples who live together in a conjugal relationship may also change their surname(s) if they 
file a form called a Joint Declaration of Conjugal Relationship.

There is no fee for this type of name change, if it is made at the time of the marriage or at 
the time of filing a Joint Declaration of Conjugal Relationship.

Please be aware that if you elect to legally change your name and were born in Ontario, this 
type of name change will result in changing your surname on your birth certificate (it will 
appear as if you were born with your married name). If you wish to revert back to your previous 
name at any time, you will need to contact the Office of the Registrar General.