Councillors met to vote on plans for a 37-week process of public consultation, aimed at deciding the road's future after prolonged debate.
However, they were informed at the meeting of a letter from Dunedin Ratepayers and Householders Association chairman Lyndon Weggery questioning the legality of the road's closure to motorists while the "protracted" consultation was carried out.
Mr Weggery's letter, a copy of which was provided to the Otago Daily Times, suggested the Reserves Act 1977 allowed only for the exclusion of all people from a reserve - not the exclusion of vehicles while other users continued to be admitted.
"It therefore begs the question whether council's action . . . could be viewed as ultra vires [beyond the council's power]."
Committee chairman Cr Paul Hudson told the meeting the letter had "given rise to a couple of questions" and staff would seek a legal opinion to have the issues clarified.
The advice was expected in time for the next full council meeting on February 22.
The road was closed last October - just two weeks after it reopened - at Mayor Peter Chin's instruction, following a death at Lawyers Head.
A small pedestrian gate in the side of the fence has allowed everyone except motorists to continue using the seaside road.
Mr Chin's actions later won retrospective approval by councillors through a vote.
Councillors late last year also voted to support plans to close the road to vehicles permanently, to improve public safety.
The report that was to be considered yesterday said consultation was required on the proposal, because the road formed part of the Ocean Beach Domain, rather than being a legal road.
It was mentioned in the domain's management plan, which also required consultation as part of any change to the plan.
The Act also required compliance with the management plan.
However, council reserves estate officer Judy Milward - the report's author - opted not to address the concerns raised by Mr Weggery's letter at yesterday's meeting until she received further advice.
Cr Bill Acklin said it appeared the Act gave the council the power to exclude all people from the reserve, but "it doesn't mention anywhere about restricting traffic".
He questioned whether the council could continue to authorise the road's closure during 37 weeks of public consultation.
Council community life general manager Graeme Hall said that would be clarified by the legal opinion being sought, but he believed other legislation covering issues of health and safety could also apply - allowing the road's current restrictions.
In this case, police had expressed concern the road was a threat to public safety, providing the basis for the council's actions, he said.
Councillors yesterday voted to begin the public consultation process, subject to the findings of the legal opinion.
The opinion would also cover whether the council could seek resource consent for a security fence at Lawyers Head during the consultation period.
