Matthew Muir KC, chairman of the fast-track panel, gave the warning in a first meeting with would-be mine firm Santana late last month, a video of the event reveals.
He said any possible breaches should therefore be considered with "high priority".
Four iwi authorities — collectively comprising Kā Rūnaka — had already raised possible treaty breaches in a January memo to fast-track authorities.
Kā Rūnaka had also raised, in the memo and a letter last November to the Environmental Protection Authority, that Santana had not met a requirement to consult with them prior to submitting its application on October 31.
Section 7 of the Fast-Track Approvals Act requires anyone using the Act to behave in ways that meet Treaty settlement obligations.
Section 11 says fast-track applicants must consult relevant iwi authorities, hapū, and Treaty settlement entities before lodging their application.
Speaking for the panel, Mr Muir was "anxious that, if there was any plausible argument that the process is foreclosed by section 7, this matter is addressed and moved up through the court structure before we spend the very significant amount of time and Santana’s money on dealing with the myriad other issues that emerge".
If breaches existed, it could be a "threshold issue" for the application, he said.
Mr Muir stressed that he did not wish to express any view on what breach concerns were held by Kā Rūnaka.
Santana had submitted its application on October 31 last year, and on November 19 Kā Rūnaka had written to the EPA — which oversees the fast track process — saying that communication undertaken by Santana prior to lodgement of its application had not constituted "proper consultation".
Case law provided principles regarding what constituted proper consultation, the letter said, including listening, considering responses with an open mind, being genuine and providing sufficient information and time to elicit "intelligent and useful responses".
The matter was important because Kā Rūnaka had "serious concerns" over the potential for "cumulative and long-term environmental effects of the proposed large mine."
The issues of environmental damage and a lack of consultation was again raised by Kā Rūnaka in a memorandum sent to panel convener Jane Borthwick on January 16, and in the context of possible breaches of Treaty.
The memo stressed "deep and immutable" concern about the effects on water, ecology, landscape and whenua, and hazardous substances remaining on the land, presenting ongoing risk of irreversible contamination.
"The Applicant’s [Santana’s] assertion that ‘granting the approvals would not breach Treaty settlements or recognised customary rights’ is not accepted. The application may constitute an ineligible activity in terms of potential breaches of Treaty settlements. This is a complex issue, made more difficult by absence of any meaningful dialogue with the Applicant on this point."
Kā Rūnaka said that consultation had been "inadequate to the point that the actions taken by the applicant [Santana] did not constitute consultation."
Santana’s legal counsel, Joshua Leckie, said in the meeting that the firm was engaging with Kā Rūnaka and in Santana’s view there were no treaty breaches.
Mr Leckie said engagement with Kā Rūnaka was "ongoing and the applicant [Santana] was conscious of the importance of that."
When prompted by Mr Muir to say something about treaty obligation requirements, Mr Leckie acknowledged Kā Rūnaka had raised "what they see are potential treaty obligation concerns but not identified to the applicant what those are — so we are not sure what they are.
"It is our case there are not treaty breaches at play here."
Santana chief executive Damian Spring said in the meeting consultation with iwi had started in 2017 and a "protocol of engagement" had been "drafted to a relatively final form but not executed".
The firm had been providing technical reports to Kā Rūnaka but it was "fair to say that a large number of them weren’t actually finalised until the application was submitted".
A draft and unendorsed cultural impact statement had been undertaken by an organisation in Dunedin.
In December, two months after Santana submitted its application, it had answered 76 technical questions asked by Kā Rūnaka.
"Engagement continues and never really ceased, " Mr Spring said.
