The comments that led to Phil Goff's removal from the job of High Commissioner to the UK were a sackable offence, a Waikato University law professor believes.
Goff publicly questioned US President Donald Trump's understanding of history at an event in London.
Foreign Affairs Minister Winston Peters said that made his continuation in the role untenable, as he was expected to support the government line.
Peters on Thursday called the decision to sack Goff one of the most difficult things he has had to do and said it was "seriously regrettable".
However, Professor Al Gillespie says it's justified.
He told Morning Report Goff was out of line.
"Mr Goff, like our diplomats and ambassadors, needs to represent the views of the country whether they agree with them or disagree with them, and right now our view with Mr Trump is one of silence, and trying not to be critical or offend him in any way," Gillespie said.
"I think the approach we've adopted is questionable, but it's okay for me to say that as a professor of law, but it's not okay for Mr Goff to say that as a representative of New Zealand government."
Gillespie said the government might be afraid of Trump's response.
"Partly the chaos, partly the reaction, because Mr Trump responds in a very vigorous way, often causing chaos around him," he said.
New Zealand would face challenges around how it responds to the war in Ukraine and whether it continued to provide support, in terms of intelligence, as well as dealing with potential agricultural tariffs from the US.
Gillespie agreed Goff's comments were a sackable offence.
Sacked ambassador Phil Goff Photo: Ricky Wilson / Stuff
"I think Phil Goff is a great New Zealander, and his understanding of history is correct.
"But, he shouldn't have expressed his view, he needs to represent the government and, especially at this time, we need tact and diplomacy more than any other point in recent history."
The comments centred on the 1938 Munich Agreement which was a peace deal forced on Czechoslovakia by the UK, France, Germany and Italy where Czechoslovakia lost some of its territory against its will.
The UK prime minister of the time, Neville Chamberlain, called it "peace in our time" but World War II began shortly afterwards.
"So what Mr Goff was alluding to was a very similar point in history."
Prof Gillespie said he was surprised by Goff's comments, and that making them in a public forum was unwise.
