Criminal Justice and Public Order Act 1949
(1) A person commits the offence of aggravated trespass if he trespasses on land in the open air and, in relation to any lawful activity which persons are engaging in or are about to engage in on that or adjoining land in the open air, does there anything which is intended by him to have the effect
(a) of intimidating those persons or any of them so as to deter them or any of them from engaging in that activity,
(b) of obstructing that activity, or
(c) of disrupting that activity.
(2) Activity on any occasion on the part of a person or persons on land is "lawful" for the purpose of this section if he or they may engage in the activity on the land on that occasion without committing an offence or trespassing on the land.
(3) A person guilty of an offence under this section is liable on summary conviction to imprisonment for a term not exceeding three months or a fine not exceeding level 4 on the standard scale, or both.
(4) A constable in uniform who reasonably suspects that a person is committing an offence under this section may arrest him without warrant.
(5) In this section, "land" does not include -
a) the highways and roads excluded from the application of section 61 paragraph (b) of the definition of "land" in subsection (9) of that section or
b) a road within the meaning of the Road (Northern Ireland) Order 1993
(Note: Sabbing on a Public Footpath across Private Land can be an offence. Running or possibly walking towards a hunt can similarly be construed as an offence)
(1) If the senior police office present at the scene reasonably believes -
a) that a person is committing, has committed or intends to commit the offence of aggravated trespass on land in the open air; or
b) that two person or more persons are trespassing on land in the open air and are present there with the common purpose of intimidating persons so as to deter them from engaging in a lawful activity or of obstructing or disrupting a lawful activity, he may direct that person or (as the case may be) those persons (or any of them) to leave the land.
(2) A direction under subsection (1) above, if not communicated to the persons referred to in subsection (1) by the police officer giving the direction, may be communicated to them by any constable at the scene.
(3) If a person knowing that a direction under subsection (1) has been given that applies to him -
a) fails to leave the land as soon as practicable, or
b) having left again enters the land as a trespasser within the period of three months beginning with the day on which the direction was given, he commits an offence and is liable on summary conviction to imprisonment for a term not exceeding three months or a fine not exceeding level 4 (currently £2,500) on the standard scale, or both.
(4) In proceedings for an offence under subsection (2) it is a defence for the accused to show
a) that he was not trespassing on the land, or
b) that he had a reasonable excuse for failing to leave the land as soon as practicable or, as the case may be, for again entering the land as a trespasser.
(5) A constable in uniform who reasonably suspects that a person is committing an offence under this section may arrest him without a warrant.
(6) In this section "lawful activity" and "land" have the same meaning as in section 68.
(Note: The offence can be summarised as 'Disobeying a Direct Order'. This is so wide ranging that even the Landowner can be excluded from his land and arrested if a Police Officer refuses to believe him)