Most treaties have termination clauses. The North Atlantic Treaty’s Article 13 provides for voluntary exit [1]. (One could argue Ankara’s SS-4 purchase constitutes an Article 8 violation, though this would be petry.)
Treaties are about mutual understanding. If Americans and Czechs would find it unseemly to fight for Turkey’s defence in case of invasion, it does more harm to pretend they’re under collective defence than to amend the treaty to make it extremely clear whom one can invade without getting nuked and whom one cannot.
All this said, I think Turkey should remain a NATO member. They have shown themselves by arming Ukraine and denouncing Putin. They are a founding member. And their position remains strategically critical.
[1] https://www.nato.int/cps/en/natolive/official_texts_17120.ht...
Okay?
> no idea what an "SS-4" is
Sorry, pre coffee. S-400.
This has been covered in the American refusal to sell Ankara F-35s and ensuing sanctioning of it under CAATSA [1].
In short, no detection system is perfect. And no modern military system is sold without servicing. Letting Russia service an air defence system with the privilege of painting NATO jets, arms and missile defences is a breach of trust. It could be considered, again, pettily, though good luck to those who claims the law is often anything but, “an international engagement in conflict with” Turkey’s NATO obligations.
[1] https://onlinelibrary.wiley.com/doi/abs/10.1111/mepo.12628