Expatriate New Zealander Hugh Morrison will see his son Trevor, 37, start work next Monday as associate legal counsel to United States President Barack Obama.

His son was born in Canada to Mr Morrison and his American wife Anne, and has used the American citizenship gained through his mother to build a career in the US.

Trevor Morrison last year moved with his wife Beth and two young daughters to Manhattan to begin work as a professor of constitutional law at Columbia University Law School.

But he has taken two years off from that job after being named as associate counsel to the president for national security affairs.

He has already worked on President Obama's first three executive orders, proclaimed the day after his inauguration to rescind the previous administration's authorisation of the Guantanamo Bay detention centre, to outlaw rendition and torture and to confine US practices to standards set by the Geneva Convention.

The high-flying career is no surprise to his father.

The New Zealander recalled his son's teachers considered him gifted.

Though the child had not had IQ tests, his results on a Grade 4 provincial assessment exam were "so far off the top of the chart that they couldn't even be accurately measured anymore," Hugh Morrison told his local paper, the Alberni Valley Times on Vancouver Island.

"We never really saw him do much homework, but when we went to talk to his teachers, they'd tell us he'd finished it all," said Mr Morrison, noting that his son had a near-photographic memory.