This is a common law offence which means that it does not come under particular legislation. The law surrounding it is from case law rather than legislation by parliament.

If you look at what must be proved that is basically what the law is in relation to this charge.

There is then a lot of case law that explains this law in greater detail.

(a) The accused did an act not authorised by law or failed to discharge a legal duty.

(b) The act either endangered the life, health, property, morals, or comfort of the public, or obstructed the public in the exercise of legal rights.

(a) Duress.

(b) Factual dispute.

(c) Honest and reasonable mistake of belief.

(d) Identification dispute.

(e) Lack of intent.

(f) Mental impairment.

(g) Necessity.