There are basically two sides to this conflict: ISIS on one hand, and the Syrian/Kurdish PYD/YPG side on the other. The latter has ties to the PKK, which is an internationally recognized terror org just like ISIS.
Now, depending on who you ask, the PYD/YPG is "good, because they fight ISIS" (e.g. the official stance of the US) or "Terrorists, because they are basically just extensions of the PKK" (what Turkey says).
This leads to a lot of inconsistency in foreign policy within NATO. For example Sweden is pressured to crack down on PYD/YPG to be admitted into NATO. The US, like many others, have supported the YPG/PYD in the fight against ISIS. So I imagine Turkey is also pressuring other NATO countries like France in this case, to go after PKK collaborators including the adjacent syrian orgs.
So basically: why are the people volunteering to fight ISIS seen as terrorists within NATO? I'd guess these days to a large extent because Turkey says so.
Now, depending on who you ask, the PYD/YPG is "good, because they fight ISIS" (e.g. the official stance of the US) or "Terrorists, because they are basically just extensions of the PKK" (what Turkey says).
This leads to a lot of inconsistency in foreign policy within NATO. For example Sweden is pressured to crack down on PYD/YPG to be admitted into NATO. The US, like many others, have supported the YPG/PYD in the fight against ISIS. So I imagine Turkey is also pressuring other NATO countries like France in this case, to go after PKK collaborators including the adjacent syrian orgs.
So basically: why are the people volunteering to fight ISIS seen as terrorists within NATO? I'd guess these days to a large extent because Turkey says so.