Protesting peacefully is not against the law as such. Climbing up a motorway gantry is against the law as it causes a public nuisance.
A person commits an offence if—
(a)the person—
(i)does an act, or
(ii)omits to do an act that they are required to do by any enactment or rule of law,
(b)the person’s act or omission—
(i)creates a risk of, or causes, serious harm to the public or a section of the public, or
(ii)obstructs the public or a section of the public in the exercise or enjoyment of a right that may be exercised or enjoyed by the public at large, and
(c)the person intends that their act or omission will have a consequence mentioned in paragraph (b) or is reckless as to whether it will have such a consequence.
(2)In subsection (1)(b)(i) “serious harm” means—
(a)death, personal injury or disease,
(b)loss of, or damage to, property, or
(c)serious distress, serious annoyance, serious inconvenience or serious loss of amenity.