Assaultive offences require an absence of consent before they are criminal. In some offences the absence of consent is presumed.
The absence of consent is determined on a subjective standard at the time the physical contact occurs. It is a question of fact determined by the trier-of-fact based on the entirety of the circumstances and the credibility of the alleged victim.
Deemed Absence of Consent
Under s. 265(3), all forms of assault, including sexual assault under s. 271, 272, and 273 cannot be consented to when the following exists:
(3) For the purposes of this section, no consent is obtained where the complainant submits or does not resist by reason of
- (a) the application of force to the complainant or to a person other than the complainant;
- (b) threats or fear of the application of force to the complainant or to a person other than the complainant;
- (c) fraud; or
- (d) the exercise of authority.
R.S., c. C-34, s. 244; 1974-75-76, c. 93, s. 21; 1980-81-82-83, c. 125, s. 19.
Section 265(3)(d) requires that there be a “coercive use of authority to overcome resistance to a consent”
Cannot Consent to Infliction of Death
In a more extreme situations, it is not possible to consent to death:
Consent to death
14. No person is entitled to consent to have death inflicted on him, and such consent does not affect the criminal responsibility of any person by whom death may be inflicted on the person by whom consent is given.
R.S., c. C-34, s. 14.
The doctrine of implied consent is based on the public policy interest to not over-criminalize certain actions. It must be "strictly limited to conduct which is consistent with the purpose and rationale underlying the policy basis".
Implied consent is not applicable to sexual assault.
R v E.(A.), 2000 CanLII 16823 (ON CA), (2000), 146 CCC (3d) 449, at paragraph 33
R v Bennett, 2006 CanLII 31012 (NL PC) at paras 41 to 45
R v Cey, 1989 CanLII 283 (SK CA), (1989), 48 CCC (3d) 480 (Sask. C.A.), at page 490
R v Ewanchuk,  1 SCR 330, 1999 CanLII 711 (SCC)
See Consent in Sexual Offences
A consensual fight is not an assault as the parties are consenting to the physical contact.  Consent can be negated or vitiated where the force causes bodily harm and was intended to be caused. Thus, where serious bodily harm was intended and caused, there can be no consent. The necessary mens rea requires that the force be applied recklessly and the risk of bodily harm was objectively foreseeable.
- R v Jobidon, 1991 CanLII 77 (SCC),  2 SCR 714
- R v Paice, 2005 SCC 22 (CanLII)
R v W.G., 1994 CanLII 3442 (ON CA), (1994), 90 CCC (3d) 139 (Ont.C.A.)
R v Jobidon at p. 22, 23
See R v Crosby 2005 PESCAD 1 (CanLII), (2005), 27 C.R. (6th) 39, 192 CCC (3d) 23 (PEI Ct. of App.) during a fist fight, consent is not vitiated unless accused intended to inflict bodily harm
- R v Sullivan, 2011 NLCA 6 (CanLII) at para 13
- Sullivan at 24
Consent in Sports
While normally a person cannot consent to an assault that intends to cause bodily harm, there is an exception to this for sports where the conduct is part of the norms of the particular sport. Thus sports players may consent to some bodily harm necessarily incidental to the sport. However, conduct that is deliberately for the purpose of inflicting injury will not be protected.
The limits of implied consent are determined by an "amalgam of written rules, unwritten code of conduct and guidelines set by a referee in a particular game". Unwritten code can include "legitimate strategy of intimidation" that involves violence.
Consent in Domestic Assaults
There is a degree of implied consent in certain social interactions such as domestic partnerships.
Consent can be used in a limited fashion for a defence to a domestic assault. There must be virtually no injury to the victim. Any injury that occurs can only be justified as an accident and not an intentional assault.
- R v Menkarios 2010 ONSC 5478 (CanLII) at para 38
- R v Shand, 1998 CanLII 4686 (NS CA), (1998), 166 N.S.R. (2d) 74 (NSCA)
R v Downey, 2002 NSSC 226 (CanLII),  NSJ No. 442 (NSSC)
R v Lewis,  OJ No. 3059 (Ont. C.J.) (*no link)
R v Swaine,  OJ No. 3457 (Ont. C.J.) (*no link)
R v Tierney,  PEIJ No. 118 (PEISCTD) (*no link)
R v Allum,  A.J. No. 360 (Alta.P.C.) (*no link)
R v Stewart,  O.J. No. 2704 (Ont.C.J.) (*no link)
R v Abraham (1974),30 CCC (2d) 332 (Que.C.A.) (*no link)
R v Bruce, 1995 CanLII 2442 (BC CA),  BCJ No. 212 (BCCA)
R v CMC,  BCJ No. 2545 (BCPC) (*no link)