The auditor-general isn't going to hold an inquiry into the granting of citizenship to US billionaire Peter Thiel.
The government granted Mr Thiel citizenship in 2011 although he had spent just 12 days in New Zealand and didn't intend to live here.
Opposition parties were outraged, and the Greens asked the auditor-general to investigate.
Cabinet minister Nathan Guy made the decision when he was minister of internal affairs, based on advice from his officials.
He used his discretion to grant citizenship "under exceptional circumstances" because Mr Thiel had made big investments in New Zealand companies and donated $1 million to the Christchurch Earthquake Appeal Fund.
Deputy Auditor General Greg Schollum has written to Denise Roche, the Green MP who asked for an inquiry, explaining why there won't be one.
"The act provides the minister with a broad discretion to grant citizenship in special cases," he said.
"The minister does not need to consider most of the normal requirements, such as presence or intention to reside in New Zealand... the success of an application will turn on the minister's assessment of 'public interest'."
Mr Schollum said the issues in the case come down to policy questions and whether the legislation strikes the right balance.
"These are not questions the auditor-general has authority to answer."
Mr Guy last month said he did the right thing when he granted Mr Thiel citizenship, and would do it again.
"This is an individual who is incredibly well connected in Silicon Valley, he's a great ambassador and sales person for New Zealand," Mr Guy said.