The Trespassers Will be Prosecuted is not saying they can’t enter, that sign is only saying if they do trespass then action may be instigated. To trespass requires a person or persons to ignore the requirement to leave when demanded or to ignore the removal of the implicit right of entry by as an example a sign that states “No Entry”.
This occurs when say leaves fall into your pool or a tree or limb of one falls into your property, or someone digs a channel under your land by failing to ensure they remained within their property line. An apology may be all that is required depending on the severity, or if the offered amount for payment of damages satisfies the Court.
From the HIGH COURT OF AUSTRALIA: PLENTY v. DILLON (1991) 171 CLR 635 F.C. 91/004 are three further excerpts:
“The general policy of the law is against government officials having rights of entry on private property without the permission of the occupier, and nothing concerned with the service of a summons gives any ground for creating a new exception to the general rule that entry on property without the express or implied consent of the occupier is a trespass.”
"A person who enters or remains on property after the withdrawal of the licence is a trespasser. In Davis v. Lisle (1936) 2 KB 434, police officers who had lawfully entered a garage for the purpose of making enquiries were held to have become trespassers by remaining in the garage after they were told by the proprietor to “get outside”. "
“True it is that the entry itself caused no damage to the appellant’s land. But the purpose of an action for trespass to land is not merely to compensate the plaintiff for damage to the land. That action also serves the purpose of vindicating the plaintiff’s right to the exclusive use and occupation of his or her land.
The appellant was entitled to resist their entry. If the occupier of property has a right not to be unlawfully invaded, then, as Mr Geoffrey Samuel has pointed out in another context, the “right must be supported by an effective sanction otherwise the term will be just meaningless rhetoric”
If the courts of common law do not uphold the rights of individuals by granting effective remedies, they invite anarchy, for nothing breeds social disorder as quickly as the sense of injustice which is apt to be generated by the unlawful invasion of a person’s rights, particularly when the invader is a government official. The appellant is entitled to have his right of property vindicated by a substantial award of damages.”
From the Domain.com.au site comes this excerpt:
"Indeed, access to your property may be more open than you imagined, as Acting Sergeant Sharon Darcy of Victoria Police points out. “Anyone has the right to walk up to a front door and knock on the door.”
Revoking the implied licence to enter is a simple matter, according to property lawyer Darren Eliau of Evans Ellis Law. He says displaying a “Do not enter” sign, “such as those available from any $2 shop”, is sufficient to prohibit entry.
“There’s no actual convention at law that says there is a certain wording that you must say. It’s not governed by any statute. It’s just what’s reasonable.
“‘Do not enter’, ‘Do not trespass’, ‘No canvassers’, ‘No hawkers’ — those types of things,” Mr Eliau says.
If there is no sign, a verbal request to leave revokes a person’s right to enter your property. Again, there is no exact wording and a vernacular indication will suffice.
Someone who has been asked to leave a property should not assume that, just because they are not hurting anybody, a shouting match is acceptable. It is not.
Mr Eliau says the usual position in law, in which a party needs to show loss before they can sue, does not apply.
“Trespass is a bit different. It is what’s called actionable per se — actionable just because you did it. You don’t need to prove a loss or damage,” he says."
The Section 2 ss 7 - 11 of the ACT Act (which is defines what a Volunteer & Community Work are) which you also referred to states the volunteer is usually not individually to be sued for loss or damages but the Organisation that employed them is, read sub section 9 of part 2.2 of Chapter 2
“(1) A liability that would, apart from this part, attach to a volunteer, attaches instead to the community organisation for which the volunteer was carrying out the relevant community work.”
However if the Volunteer acted in certain ways then the Volunteer becomes liable not the organisation. It doesn’t absolve the act of trespass it just makes clear which of the person/s or organisation is the one to be held accountable.
ss10 just sets forth that the ACT Govt may take responsibility instead of the organisation when and only if that orgainsation is undertaking a “recognised government responsibility [which] means a responsibility prescribed by regulation as a recognised government responsibility.” This is not party political door knocking.
ss11 is setting forth that the ACT Govt may require that community organisations are to obtain insurance to cover for liabilities from damages caused.
And then in Chapter 10 section 141
“Defence to action for trespass to land
It is a defence to an action for trespass to land if the defendant
(a) the defendant does not claim any interest in the land; and
(b) the trespass was because of negligence or was not intentional;
© the defendant made a reasonable offer to make amends to the
plaintiff before the action was brought.”
The 3 and’s set the parameters in that all parts must be satisfied to grant a defence. Thus if the entry was intentional (for example ignoring the “No Entry” sign) the defence fails. If they have not made a offer of amends the defence fails.
If the person does not leave your land you can use reasonable force to remove them or just ring the police and they will remove them. Be careful how much force you use if you try to remove them as it can easily become an assault if you over exert. If they have entered in contravention of your explicit refusal of entry eg a sign, locked gate, you can ask the police to prosecute the offender.