Cancelling passports: A conundrum

The Countering Terrorist Fighters Bill adds to the government's powers to cancel a person's passport, even if overseas, if there is reason to believe that the person is a danger to the security of New Zealand because the person intends to engage in a terrorist act. So, here's a scenario for you to think about.
Suppose two NZ'ers, Alex and Kim, are planning to travel overseas, ostensibly as tourists. Alex flies to Vienna, but has a visa to enter Ukraine. Kim flies to Moscow.
Alex then travels by land to Ukraine to enlist as an international volunteer with the Right Sector militia. This is an ultra-nationalist militia that is supported by the Ukrainian Interior Ministry and which engages in Ukraine's 'anti-terrorist' campaign in the eastern provinces of Lugansk and Donetsk. These 'anti-terrorist' forces have been fighting separatist rebels for many months now, and the Ukrainian armed forces have been responsible for the deaths of many hundreds of unarmed Ukrainian civilians.
On arriving in Moscow, Kim heads south and crosses the very porous border into Donetsk province to join the pro-Russian rebel forces there. These forces too have been responsible for the deaths of many innocent civilians (including, in all probability, the passengers and crew of MH17).
So, whose passport should be cancelled? Alex's, for joining a neo-fascist militia that kills and terrorises innocent people; or Kim's, for joining an armed uprising that has been labelled 'terrorist' by the same government that supports the neo-fascist Right Sector and that has been killing its own citizens? Or neither? Or both? Is either person 'a danger to the security of New Zealand'?