S.137(1) Highway Act 1980: a summary offence
Definition: "If a person, without lawful authority or excuse, in any way willfully obstructs the free passage along a highway he is guilty of an offence and liable to a fine not exceeding (level three on the standard scale)."
Power of arrest for this offence is only available where the general arrest conditions of Police and Criminal Evidence Act 1984 are satisfied.
Any usage of the highway which diminishes the space available to the public for passing and repassing is primia facie an obstruction.
However it is well established that there is no need to prove actual obstruction in the sense that any particular persons were inconvenienced, although the latter feature does have a bearing on the question of the reasonableness of the use of the highway by the defendants.
"Without lawful authority or excuse": in the context of sabbing it is the defence of "reasonable use" which will amount to the lawful excuse - plainly a reasonable use of the highway cannot amount to an offence under this section.
To decide whether or not an obstruction is reasonable and therefore excused relies upon factors such as
Note in Hirst vs Chief Constable, West Yorkshire (1987) an Animal Rights case, the judge said that: "freedom to protest on issues of public concern would be given the recognition it deserves"
In this case the court said that if the obstruction was incidental to the rights of passing and repassing the conduct was not an offence.