Those complaints set in motion IPENZ's disciplinary procedure, which found the they should be referred to a Disciplinary Committee.
Mr Harding resigned his membership of IPENZ on June 25.
At the start of the disciplinary hearing, Mr Harding objected to the organisation's jurisdiction in light of his resignation, the decision said.
However, IPENZ proceeded with the hearing on the basis it did have jurisdiction. Last month, it released its ruling on the complaints.
Its substantive decision in relation to the complaints has been stayed subject to the High Court ruling.
Mr Harding told the court that IPENZ's jurisdiction was limited only to current members, the decision said.
"He contends that rights of appeal are limited to current members and, as he no longer has membership, he cannot request an appeal from the decision of the Committee."
IPENZ said the disciplinary procedures related to the complaint or the member's conduct, and it was an individual's membership status at that time which related to the question of jurisdiction, not at the time of hearing, the decision said.
"IPENZ submits it is sufficient that at the time of the conduct giving rise to the complaints and when the complaints were made that Mr Harding was a member of IPENZ."
Justice Cameron Mander said Mr Harding became a member of IPENZ in 1985 and he was "cognisant of the obligations and responsibilities" that attached to that membership.
"As already observed, the conduct the subject of the complaints occurred at the time of his membership, as did the complaints."
Mr Harding would also be able to appeal against any ruling that came from the disciplinary hearing, Justice Mander said.
The appeal for a judicial review was dismissed.