This article is from the can.talk.guns FAQ, by Skeeter Abell-Smith firstname.lastname@example.org with numerous contributions by others.
Not only can you defend your life with deadly force, but you may defend
your home. Sections 32 and 40 of the Criminal Code (CC) allow use of
1) where you fear death or grievous bodily harm, and
2) to keep persons from illegally entering your home.
Colet v Regina (CCC vol. 57, 2d, pages 105 to 113, Jan 27, 1981) is the
most recent example of the latter that I have found. Briefly, the local
police tried to enter Mr Colet's home in Prince Rupert, BC, without a
warrant to do so. (They had only a warrant to seize whatever weapon he
might have had.) He violently denied entry, even throwing Molotov
cocktails at the police. Mr Justice Ritchie wrote in the _unanimous_
Supreme Court of Canada decision:
"The common law principle has been firmly engrafted in our law since
Semayne's case (1604) as reported in 5 Co. rep. 91a 77E.R. 194 where
it was said [at p. 91b]: ``that the house of every one is to him as
his castle and fortress, as well for his defence against injury and
violence, as for his repose...''. This famous dictum was cited by
my Brother Dickson in the case of Eccles v Bourque et al (1974), 19
CCC (2d) 129, 50 D.L.R. (3d) 753,  2 S.C.R. 739, in which he
made an extensive review of many of the relevant authorities."
However, it is likely far better to use the protection offered by
sections 494, 25 and 29 of the Criminal Code (CC) of Canada. They
"marry" to offer major protection to any person who is trying to
_arrest_ a criminal, or a person he or she believes on reasonable
grounds to be a criminal _and_ a threat of death or grievous bodily
harm. They also protect him or her if force is used because the
person being arrested is resisting arrest.
When dealing with any home invasion (or other criminals) the _first_
words out of your mouth should _always_ be, "YOU ARE UNDER ARREST!"
If the intruder then assaults _you_, he has _no_ justification. He
is resisting arrest, and that is a crime under CC s. 270. One
should also read CC s. 265, 267, 268, and 270(1)(b) to clarify the
above sections. CC s. 27, 34, 36, 37, 38, 39, 40, 41, 42, 43, 44,
and 45 should be read by every person interested in what one can and
cannot do in the areas of self-protection and control of doubtful