It is thought the agency accesses Auckland Transport's cameras. Photo: RNZ / Cole Eastham-Farrelly
The SIS says it has received legal advice on its use of CCTV cameras that backs its approach.
The security and intelligence watchdog last year told the spy agency to review and revise its legal basis for accessing video footage shot by other agencies.
The Crown Law advice was legally privileged so could not be revealed, but supported what it did, the SIS told RNZ.
It is thought the agency accesses Auckland Transport's cameras.
The Inspector-General of Intelligence and Security told the SIS last year it has previously been too secretive about using CCTV - to the point the camera network's unidentified owner was not allowed to keep a copy of the deal that gave the spies access to it.
The SIS said all the watchdog's other recommendations had now either been fully addressed or were underway.
It had taken steps to bolster its CCTV record keeping and updated the Memorandum of Understanding with the network owner to clarify why it needed access.
"Further policy updates are well underway," it said in a statement.
The 2021 inquiry found it used CCTV in a lawful, "responsible and proper manner".
The report noted that access to CCTV was an obvious and important tool for intelligence agencies.
"The NZSIS continues to access CCTV footage in accordance with its functions and the law."