The use of force or violence by one person against another person is unlawful according to common law, without a reasonable excuse.
Unlawful use of force or violence attracts criminal penalties, depending on the level of force or violence used.
Such misbehaviour can also attract civil penalties: that is, the right of an individual to sue for loss, injury and damage as a consequence of any injury caused by the perpetrator of that force or violence.
The use of force by police officers may be unlawful if it is not justified at all in the circumstances of the protest or demonstration. It may also be unlawful if the amount of force used is excessive and dangerous.
The Victoria Police Manual provides guidance about Victoria Police policy regarding the use of force. The philosophy said to apply to the planning, implementation and evaluation of all police operations is that the success of an operation should be primarily judged "by the extent to which the use of force is avoided or minimised". (Victoria Police Manual, Instruction 101.1 Operational Safety Principles).
The policy emphasises a range of response options which do not require the use of force and avoid confrontation.
If the force used by a police officer is not reasonable and/or breaches Victoria Police guidelines and the common law, a person injured as a consequence of that force may be entitled to sue the police officer and the officer's employer (generally the State or Federal Government) in tort.