Criminal Code, Sections 34-37

34. (1) Every one who is unlawfully assaulted without having provoked the assault is justified in repelling force by force if the force he uses is not intended to cause death or grievous bodily harm and is no more than is necessary to enable him to defend himself.

(2) Every one who is unlawfully assaulted and who causes death or grievous bodily harm in repelling the assault is justified if
(a) he causes it under reasonable apprehension of death or grievous bodily harm from the violence with which the assault was originally made or with which the assailant pursues his purposes; and
(b) he believes, on reasonable grounds, that he cannot otherwise preserve himself from death or grievous bodily harm.

35. Every one who has without justification assaulted another but did not commence the assault with intent to cause death or grievous bodily harm, or has without justification provoked an assault on himself by another, may justify the use of force subsequent to the assault if
(a) he uses the force
     (i) under reasonable apprehension of death or grievous bodily harm from the violence of the person whom he has assaulted or provoked, and
     (ii) in the belief, on reasonable grounds, that it is necessary in order to preserve himself from death or grievous bodily harm;
( b) he did not, at any time before the necessity of preserving himself from death or grievous bodily harm arose, endeavour to cause death or grievous bodily harm; and
(c) he declined further conflict and quitted or retreated from it as far as it was feasible to do so before the necessity of preserving himself from death or grievous bodily harm arose.

36. Provocation includes, for the purposes of sections 34 and 35, provocation by blows, words or gestures.

37. (1) Every one is justified in using force to defend himself or any one under his protection from assault, if he uses no more force than is necessary to prevent the assault or the repetition of it.
(2) Nothing in this section shall be deemed to justify the wilful infliction of any hurt or mischief that is excessive, having regard to the nature of the assault that the force used was intended to prevent.