This is a common question for those contemplating a separation from their partners.
The answer is both yes and no, depending on your individual situation. If you're married, and the premises to which you're seeking to change the locks is a matrimonial/family residence, then the answer is no. There can be more than one matrimonial/family residence, and this can include rental premises as well as owned premises, whether or not you are the sole owner.
If you are common law or cohabiting, then the answer is yes if you are the owner, but no if you are not a registered owner. In common law/cohabiting situations, there is not a right of possession as there is among married people, and therefore no prohibition against locking the other person out. This prohibition is negated if an agreement, court order, or other presumptive action shows an intention to give up the right of possession. Giving up the key may be sufficient to show a waiver of the right of possession.
Same-sex partners have the same rights as other cohabiting couples in this regard -- but none of the rights of possession of marriage unless there is ownership. Joint ownership conveys equal rights of possession and ownership to both spouses or partners.
If there is a potential for violence or the simple unwillingness to share a bed, I am more and more of the opinion that to lock a bedroom does not offend the provision of the Family Law Act. It may be simple, reasonable self-preservation, especially if there's more than one bedroom available in the home. Make sure the other person calls the police. Be calm and explain that you are protecting yourself but not locking the other person out of the premises.
If there is violence, call the police and they will, in the face of actual violence or provable threats, remove the other party. Be prepared to approach the family courts for a court order of exclusive possession of the premises and furnishings.
Judith Holzman is a collaboratively trained family lawyer who has practiced for over 33 years in the Toronto and York Region area. She has participated in amendments to the Family Law Act (provincial) and the Divorce Act (federal) in the area of religious divorce.