Justice Minister Andrew Little says the government has tools to use against citizens like "Kiwi Jihadist" Mark Taylor.
Taylor, who was born in Hamilton, is in a Syrian prison after surrendering to Kurdish troops.
Andrew Little told Mike Hosking there are options for legal action if he does manage to return to New Zealand.
"We have the means to deal with some of what he's done here, it will be up to the authorities to decide what they do in terms of prosecution...but we can deal with that."
"There is enough stuff that he has publicly admitted to doing that we know gives the authorities grounds here to at least investigate.
However, he agreed with the Prime Minister saying at the end of the day he "is a citizen".
"This is a pretty unsavoury character...but he is a New Zealand citizen and if he wants to come back here, we couldn't stop him coming back here."
"We can't stop him coming back here if he wants to but we do have the means to deal with him and keep New Zealanders safe."
Little said New Zealand has signed various agreements saying they won't make stateless people.