Sometimes the common law recognises that uninvited entry onto another person’s (the occupier’s) private property is not trespass. An implied licence is given, in some circumstances, to strangers to enter on private property to speak to the occupier. This usually, in the suburbs, involves going through a gate, walking up a path to the front door, and knocking. In a more urban environment it can mean just entering a vestibule and pushing a doorbell intercom. Or even just pushing a button if there is no vestibule. It is the existence of the gate, path and front door, or the bell, from which the occupier’s permission to enter is implied.
This common law implied licence can be revoked by an occupier. A sign prohibiting entry may be displayed. The person may be told to leave. The occupier may simply not answer the door knock or bell push. If the visitor does not leave, a trespass is committed.
The traditional justification for the implied licence has been protection of the occupier’s property rights against undesired entry by everyone else, including officials of the state. Whether an implied licence exists has traditionally been determined according to what the visitor is seeking to achieve by entering. This is because permission to enter would not be implied if the occupier would not have wanted to receive a visitor who had an adverse purpose. In this sense it is a subjective assessment.
For example, an implied licence would not authorise an official, entering without any legislated authority, to coerce an occupier to give information. But a purpose of seeking the occupier’s voluntary cooperation would be within the licence.
Some revision of the legal basis for implied licences has occurred. Under this revision, implied licences exist for pragmatic reasons, not because of what an occupier would want, but because of the way society works today. This is an objective justification for implying the licence to enter.
A consequence of this revision is that where the person entering has both a traditionally legitimate reason for entering (that is, a reason to which the occupier would not object) and a traditionally illegitimate reason (that is, a reason that is objectively reasonable although not one that the occupier would have been assumed to like), the entry is not a trespass but is protected by the implied licence, subject always to revocation. To both check on well-being, and if the circumstances arise, to compel release of information, can be within an implied licence: Roy v O’Neill  HCA 45 (9 December 2020).
The Court split 3-2 on this. Two majority judgments were delivered, by Kiefel CJ and jointly by Keane and Edelman JJ. The joint dissenters were Bell and Gageler JJ. The dissent was on both the law and the interpretation of the evidence.
Bell and Gageler JJ summarise what I have called the traditional or subjective basis for an implied licence:
“ The implied licence to ‘knock and talk’ is accordingly confined by reference to the ‘purpose’ of the visit, in the sense that the status of an uninvited visitor as either a licensee or a trespasser depends on what the visitor is seeking to achieve at my home by walking up my path, standing at my doorstep and knocking on my door. If the purpose is just to talk to me, and in talking simply to ask for permission to come inside or to go elsewhere on my land or simply to ask for my voluntary cooperation in pursuing some inquiry, the totality of the conduct is within the scope of the licence. If the purpose is just to coerce me, the totality of the conduct is outside the scope of the licence; it is a trespass.”
And as to visitors with mixed purposes,
“ ... the answer lies in identifying the limits of the permission granted by the implied licence to ‘knock and talk’. The preferable view is that a police officer who walks up my path, stands at my doorstep and knocks on my door exceeds the limits of the permission granted by the implied licence, and is therefore a trespasser, if the police officer has any conditional or unconditional intention of ordering me to do anything. That view is preferable because it is clear and workable and because it is consonant with contemporary community expectations. At this stage in the development of the common law of Australia, it is an appropriate resolution of the ‘contest between public authority and the security of private dwellings’ [citing Kuru v New South Wales(2008) 236 CLR 1 at 15 , quoting Halliday v Nevill (1984) 155 CLR 1 at 9.]”
The objective basis for the implication of a licence to enter private property was put by Keane and Edelman JJ as being akin to a presumption:
“ ... it is based upon ‘an incident of living in society’ [citing Halliday v Nevill (1984) 155 CLR 1 at 19], ‘the reasonable requirements of society’ [citing Tararo v The Queen  1 NZLR 145 at 172;  NZSC 157 at ], ‘the habits of the country’ [citing McKee v Gratz (1922) 260 US 127 at 136], or ‘background social norms’ [citing Florida v Jardines (2013) 569 US 1 at 9].”
Plainly, citation of those authorities makes it appear that what I have called the revised or objective approach is really long-established. However, in Tararo at - the joint judgment by Blanchard, Tipping, McGrath and William Young JJ points out that originally the licence was based on the implied consent of the occupier (that is, it was what I am calling subjective), and more recently, to accommodate such things as undercover police operations, a “more satisfactory legal basis” is that the licence is implied by law to permit entry for reasonable inquiry, subject to revocation.
The move from subjective to objective justification for implication of a licence to enter private property accommodates the “mixed purpose” visitor, subject to express revocation (Kean and Edelman JJ at -).
Kiefel CJ accepts the objective justification for recognition of implied licences (at ). The law implies the occupier’s permission as a socially desirable limitation on the law of trespass. Importantly, the purpose of entry must involve “no interference with the occupier’s possession nor injury to the occupier” (at , ).