There isn't a pressing need to ban NA, it is just theatre. The state has a tonne of methods at its disposal to crack down on small groups and it has the resources to do it too. As others have said, they can ban NA and tick the box of "having done something". Then watch the ripples of recrimination spread across the far right pond.
My guess would be that if they had a shopping list that they would also try and ban some Islamic groups or if they were particularly desperate they could find some people who are supporting anyone who goes out to fight ISIS on the basis that they are connected to weaponry in some way. Or manufacture some spurious group connected to the Informal Anarchists or whoever the fuck they were?