Highways Act 1980.
Here we will look at sections 132 and 137 of the Highways Act 1980. To the best of the author’s knowledge, section 132 is rarely used against activists. It provides the offence of placing an Unauthorised Marks (signs, letters, inscriptions and so on) on Highways and it is possible that it would be used against someone caught doing a banner drop over a road bridge, for example. Arrests under s137 (Willful Obstruction of the Highway) are sometimes threatened by the police when dealing with people doing street stalls or demonstrations. Unless you are actually obstructing the highway by positioning your stall or yourselves badly, it is unlikely that the case would go anywhere. The author has friends who were convicted for willfully obstructing the highway by doing a street stall, but this conviction was overturned upon appeal as the stall took up 2 -3 feet of a pathway more than 7 feet wide.
Of course, section 137 is also used against activists doing road blockades, etc. where the purpose is to actually obstruct the highway as a tactic. The penalty for this offence is a fine and not imprisonment.
Section 132 – Unauthorised marks on highways.
(1)A person who, without either the consent of the highway authority for the highway in question or an authorisation given by or under an enactment or a reasonable excuse, paints or otherwise inscribes or affixes any picture, letter, sign or other mark upon the surface of a highway or upon any tree, structure or works on or in a highway is guilty of an offence and liable to a fine not exceeding £100 or, in the case of a second or subsequent conviction under this subsection, to a fine not exceeding £200.
(2)The highway authority for a highway may, without prejudice to their powers apart from this subsection and whether or not proceedings in respect of the matter have been taken in pursuance of subsection (1) above, remove any picture, letter, sign or other mark which has, without either the consent of the authority or an authorisation given by or under an enactment, been painted or otherwise inscribed or affixed upon the surface of the highway or upon any tree, structure or works on or in the highway.
Section 137 – Penalty for willful obstruction.
(1)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 3 on the standard scale.