According to the Nato agreement, if one member state is attacked, all member states must come to its defense. So what if a state is attacked from within, in a plot orchestrated from within another Nato country? That appears to be the case with the attempted coup in Turkey on July 15th. Even if we generously assume that the US did not itself participate in the plot, the leader of the group responsible for the attempted overthrow of the Turkish government is in their country.
By Nato’s rules, shouldn’t the US, and Turkey’s other Nato allies, regard the Gulen movement as a hostile non-state actor responsible for an attack on a Nato member? Extradition, in this case, would seem to be the least of what the US is required to do. If what happened on July 15th had been carried out by a foreign military, the country responsible for the attack would find itself at war with every country in the Nato Alliance. Yet, when you are talking about a Fifth Column within a country, whose activities are being coordinated from abroad, apparently, there is a loophole
A Nato country, like the US, can give safe haven to a group that attacks its Nato ally, without any legal repercussions; and the Nato Alliance has no responsibility to defend a member state from aggression planned externally, as long as the action is carried out by internal actors.