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.

(b) The persons had commenced to execute their common purpose, but had not completed its execution.

(c) The accused was a member of those persons assembled.

(d) The accused intended to help the other persons assembled, by force if necessary, against any person who might oppose the assembly in the execution of its common purpose.

(a) Duress.

(b) Factual dispute.

(c) Honest and reasonable mistake of belief.

(d) Identification dispute.

(e) Lack of intent.

(f) Mental impairment.

(g) Necessity.