Canada does not really have any hard and fast rules, with regard to knives. Specifically, except for lists of a few specifically banned styles they do not even mention them. And something that must be kept at the top of your mind at all times is that a knife is not necessarily a weapon.
There are specific lists and descriptions, but suffice it to say you cannot own any gang knifes of knifes designed to be concealed. Specifically, knives that have easy/auto opening abilities are, for the most part, banned or a legal gray area.
The letter of the law pretty much allows you to carry any blade of any size anywhere, as long as you are not going to commit a crime with it, but if it could be considered a weapon it cannot be concealed. Not concealed is a matter of perspective as well; are you transporting your knife in your backpack, or are you concealing it; It depends on the circumstances and the perspective.
In real life cops do not like knives that are too big or too scary looking. If they think you having that knife is dangerous to the public good they will take it away from you, at the very least. I have heard numbers up to 6 inch as being the maximum allowed, but some cops will have a problem with far smaller knifes. It is all about where you are, what you look like, what you are doing, and does the knife look like a tool or a weapon.
Also it is important to know that, while I was completely unable to find any law pertaining to this, Canadian law enforcement do not allow the carrying of self defensive objects. If they believe your knife is for self defence, or you tell them it is, supposedly it will be taken away. The criminal code seems to specifically allow defensive weapons, but I am no law expert. If you happen to have a knife handy for a different reason (non self-defensive reason), and can prove that, you can use it when in danger of your life from an assailant.
Criminal Code, relevant quotations:
Prohibited Weapons
(a) a knife that has a blade that opens automatically by gravity or centrifugal force or by hand pressure applied to a button, spring or other device in or attached to the handle of the knife.
88. (1) Every person commits an offence who carries or possesses a weapon, an imitation of a weapon, a prohibited device or any ammunition or prohibited ammunition for a purpose dangerous to the public peace or for the purpose of committing an offence.
89. (1) Every person commits an offence who, without lawful excuse, carries a weapon, a prohibited device or any ammunition or prohibited ammunition while the person is attending or is on the way to attend a public meeting.
90. (1) Every person commits an offence who carries a weapon, a prohibited device or any prohibited ammunition concealed, unless the person is authorized under the Firearms Act to carry it concealed.
Weapon
“weapon” means any thing used, designed to be used or intended for use
(a) in causing death or injury to any person, or
(b) for the purpose of threatening or intimidating any person
Carry
'88. (1) Every person commits an offence who carries or possesses a weapon, an imitation of a weapon, a prohibited device or any ammunition or prohibited ammunition for a purpose dangerous to the public peace or for the purpose of committing an offence.
89. (1) Every person commits an offence who, without lawful excuse, carries a weapon, a prohibited device or any ammunition or prohibited ammunition while the person is attending or is on the way to attend a public meeting.
90. (1) Every person commits an offence who carries a weapon, a prohibited device or any prohibited ammunition concealed, unless the person is authorized under the Firearms Act to carry it concealed.
Use on another Person
'17. A person who commits an offence under compulsion by threats of immediate death or bodily harm from a person who is present when the offence is committed is excused for committing the offence if the person believes that the threats will be carried out and if the person is not a party to a conspiracy or association whereby the person is subject to compulsion, but this section does not apply where the offence that is committed is high treason or treason, murder, piracy, attempted murder, sexual assault, sexual assault with a weapon, threats to a third party or causing bodily harm, aggravated sexual assault, forcible abduction, hostage taking, robbery, assault with a weapon or causing bodily harm, aggravated assault, unlawfully causing bodily harm, arson or an offence under sections 280 to 283 (abduction and detention of young persons).
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.
Marginal note:Extent of justification
(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.
