Philip Blackwood with partner Noemi Almo, before he was arrested.

He should be a free man, but Philip Blackwood is still behind bars thanks to Australian immigration laws.

The Wellington man has been locked up in Myanmar's notorious Insein Prison, in Yangon, for 13 months after being convicted under religious laws for posting an image of Buddha in headphones on Facebook.

Last week he was finally given a presidential pardon by Myanmar's government. But while his parents couldn't wait to get him home, to their frustration Blackwood has still not been released, as his flights home through Sydney have been rejected by the Australian government.

Blackwood's father, Brian Blackwood, said the New Zealand High Commission in Yangon went to see Philip last Friday, explaining to him he would be getting flights on Monday and be back in New Zealand on Tuesday.

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Brian booked his son home first-class to arrive on a flight with his fiancee and baby daughter.

But when Australian Immigration found out Blackwood was due to transit through Sydney, they rejected his entry due to his criminal conviction, Brian said.

"The Australians have blocked him from travelling through. Good God, he's a political prisoner, it's neverending," Brian said.

If he were to fly through Australia he would need a special pass, which could take weeks to process, he said.

An Australian Department of Immigration and Border Protection spokesman said it held no information suggesting a "formal request" was made for Blackwood to transit Australia.

It said no such request was denied.

While Blackwood was told he would be released Monday, the day before his 34th birthday, he will stay in his cell until he can fly home via another route.

The release had already been delayed after the prison lost Blackwood's passport.

"They wont let him out of the prison, but he's a free man," Brian said.

"He had been given amnesty in the prison and now they're playing silly buggers with him ... I imagine his mind's all over the place, he's suffered enough," he said.

Blackwood lost more than 20kg during his 13-month incarceration at the Myanmar prison, since being arrested on December 10, 2014 for insulting religion.

He was sentenced to 30 months imprisonment with hard labour after posting an image of Buddha in headphones on social media to promote a cheap drinks night at a bar he worked at.

However, last week he was among 101 political prisoners due to be freed by Myanmar's government in a presidential pardon.

A spokesman for the Ministry of Foreign Affairs and Trade would not comment on Tuesday morning on Blackwood's still being imprisoned.

"The New Zealand Embassy in Myanmar was continuing to liaise with the relevant authorities over the amnesty release arrangements and Mr Blackwood's family regarding deportation details," he said.

The Australian High Commission has been contacted for comment.