Criminal Code 2002

A person is not criminally responsible for an offence if the person carries out the conduct required for the offence in self-defence.

A person carries out conduct in self-defence only if—

the person believes the conduct is necessary—

to defend himself or herself or someone else; or

to prevent or end the unlawful imprisonment of himself or herself or someone else; or

to protect property from unlawful appropriation, destruction, damage or interference; or

to prevent criminal trespass to land or premises; or

to remove from land or premises a person committing criminal trespass; and

the conduct is a reasonable response in the circumstances as the person perceives them.

However, the person does not carry out conduct in self-defence if—

the person uses force that involves the intentional infliction of death or serious harm—

to protect property; or

to prevent criminal trespass; or

to remove a person committing criminal trespass; or

the person is responding to lawful conduct that the person knows is lawful.

Conduct is not lawful for subsection (3) (b) only because the person carrying it out is not criminally responsible for it.