A counter-terrorism expert says there would be little to no long-term risk if we allowed 'Kiwi Jihadist' Mark Taylor to return home.

The New Zealand Islamic State fighter has been captured by Kurdish forces in Syria.

George Washington University's David Mallett has tracked hundreds of westerners who have returned home after fighting for IS.

He told Mike Hosking they have a low chance of further radical actions, particularly in the long-term.

"I've done some research...looking at hundreds of returnees from Jihadi groups and it turns out there is no long-term threats of sleeper cells, if someone is going to try a terrorist attack at home, they do it within the first few months or not at all."

"So we need to target law enforcement  and perhaps rehabilitation services into a short term problem."

Mallett said the long-term threat is the Jihadis that don't come home and instead travel from war zone to war zone. 

"The longer-term threat is keeping an eye on the ones who might show up in other places."

However, he said he understands the fear and anger Taylor is stirring up.

"I certainly wouldn't want Mark Taylor as a neighbour myself at this point, but on the other hand, I think national security decisions shouldn't be based on what makes us angry, but what makes us safe."

Mallett said Taylor is a unique case because this isn't the first time he has done something like this.

"This issue for Mark Taylor, in particular, is that we have been through this with him before already, he tried to join Al-Qaeda in the past before ISIS came along and Australia deported him and look where he ended up."

"So we have to ask ourselves the question, for all these hundreds of foreigners who're being held right now by the Kurds and other groups, do we trust them to watch our Western citizens indefinitely and what happens when they let them go."

"When it comes to foreign safety, it's not really a question of what the foreign fighters deserve but what the rest of us deserve."

He said this is  a problem plaguing a number of countries, and no one really knows how to handle it."

"Most Western countries are grappling with this problem. We don't have a precise sense of how many foreign fighters there are out there. So this is a problem we are going to have to deal with for a long time to come."

"Under international law, every country is supposed to repatriate and prosecute its citizens but there are no guidelines for what they are supposed to do with them," he said. 

 

"It's something that comes up on a case by case basis."

 

Mallett said there is certainly enough video evidence showing him supprting a terrorist organisation for him to be charged.