Technically, the refusal of entry to a bar amount to a revocation of the implied licence for a member of the public to enter the premise. At that point, the person refused entry, should they remain, commits a trespass. Pubs and bars are private businesses and they at first blush appear to have the right to determine who can enter their premises or not. However, it may not be as simple as that.
The sale of alcohol to the public is an activity that is tightly regulated. You cannot serve alcohol to the public without meeting strict regulatory criteria. You must be licenced to supply and serve alcohol.
Arguably the Human Rights Act 1993 applies:
133 Licences and registration
(1) Where any person is licensed or registered under any enactment to carry on any occupation or activity or where any premises or vehicle are registered or licensed for any purpose under any enactment, and where the person or other authority authorised to renew, revoke, cancel, or review any such licence or registration is satisfied—
This being so, a bar or pub clearly conduct a business that requires a licence pursuant to the Sale of Liquor Act 1989. Part 2 of the HRA states:
(1) The only provisions of this Part that apply to an act or omission of a person or body described in subsection (2) are—
Section 5 of the BORA provides that the rights and freedoms contained in the Act may be subject only to such reasonable limits prescribed by law as can be demonstrably justified in a free and democratic society.
In determining whether a limitation on a right is “demonstrably justified”, the Court of Appeal in its Moonen decision set out its own test to determine whether or not a limitation is “demonstrably justified” (Moonen v Film and Literature Board of Review (1999) 5 HRNZ 224, 234 Para ):
1) Identify objective which the Legislature was endeavouring to achieve by the provision in question;
2) Assess the importance and significance of that objective;
3) The way in which the objective is statutorily achieved must be in reasonable proportion to the importance of the objective;
4) The means used must also have a rational relationship with the objective;
5) In achieving the objective there must be as little interference as possible with the right or freedom affected;
6) The limitation involved must be justifiable in light of the objective.
In Moonen the Court stated, “where an enactment can be given a meaning that is consistent with the rights and freedoms contained in the Bill of Rights, that meaning shall be preferred to any other. Thus if there are two tenable meanings, the one which is most in harmony with the Bill of Rights must be adopted” (Moonen v Film and Literature Board of Review (1999) 5 HRNZ 224, 233 Para ).
The Moonen test underwent a slight refinement in Hansen v The Queen  NZSC 7;  3 NZLR 1; (2007). The majority of the Court approved the methodology of Richardson J in Noort. McGrath J gave the most thorough outline of the approach to be taken, which was broadly consistent with that of Blanchard, Tipping and Anderson JJ (at ). The Court recognised that an obvious first step was to ascertain whether there was a prima facie conflict between an enactment and a Part II right (at ).