In Plenty v Dillon (1991) HCA 5 the High Court of Australia held that police officers who entered the appellant’s farm to serve a summons did not have express or implied consent for entry and therefore committed a trespass.
This case is often wrongly cited by various theorists, as if it applies to police officers who do actually have the statutory authority to enter premises in certain situations. The case relates to the serving of a summons, of which there is no statutory source of power to enter premises against the wishes of the occupier. In paragraphs 5 and 6 the court recognises that besides the common law exceptions to the tort of trespass:
“a number of statutes also confer power to enter land or premises without the consent of the occupier. But the presumption is that, in the absence of express provision to the contrary, the legislature did not intend to authorize what would otherwise be tortious conduct.”
As Brennan J said in Halliday v Nevill (1984) HCA 80, (a passage later approved by the High Court in Plenty v Dillon):
“The principle applies alike to officers of government and to private persons. A police officer who enters or remains on private property without the leave and licence of the person in possession or entitled to possession commits a trespass and acts outside the course of his duty unless his entering or remaining on the premises is authorized or excused by law.”
When the action is actually “authorized or excused by law” and the officer is acting under statutory powers in the execution of his duties, citing Plenty v Dillon will get you nowhere, and using force to prevent them from doing so will likely result in obstruction charges. The Police Powers and Responsibilities Act of the particular State confers power to enter land or premises without the consent of the occupier in certain situations, and also provides the relevant legislation relied upon.