During that time he helped advise the Labour Government on the Supreme Court's structure, as it replaced the London-based Privy Council, so it was fitting Sir Terence was appointed to that court in 2013.
As Solicitor-General he appeared before both of those benches, representing the Crown.
In court, he'll remain Justice Arnold, but he thinks his official title will be Justice Sir Terence Arnold.
"It's a great thrill. It's a recognition, I think, of the roles that I have played, but particularly the role of the Supreme Court," he said of the knighthood.
"New Zealand's a constitutional democracy. We have a strong commitment to the rule of law and the court which ultimately has the responsibility for that is the Supreme Court.
"The cases we get are difficult cases and it's in a sense where the rubber hits the road, where the rule of law is upheld to the best of our ability. I think that's the importance of it."
Sir Terence lives in Wellington with his wife, who becomes Lady Susan.
"She's quite chuffed about it.
"I'm most pleased for my mother [Joyce], who was 94 on Christmas Day. She's still as bright as a button."
Away from the law, sailing is Sir Terence's passion. He said a "must do" of his was an ocean voyage, something he ticked off with a trip to Vanuatu.
Sir Terence hails from Canterbury, but moved to Wellington to study law.
From 1970 to 1982 he taught at law schools in New Zealand and Canada.
He was a partner at Chapman Tripp Sheffield Young between 1985 and 1994, before moving out on his own and being appointed a Queen's Counsel in 1997.
