Where Does The Law Stand In S-400 Versus F-35 Case?

A long-standing discussion on Turkey's S-400 surface to air missile system ('S-400') procurement from the Russia is again a topical issue in Turkish-US relations while parties are continuing to negotiate.  Several NATO Allies, notably the United States, have been nudging Turkey many times through hectoring speeches although the arguments were not entirely based on legal perspective. Considering spoken countermeasures against the Turkey, such as sanctions, it is easy to say that the effect on the ongoing F-35 Joint Strike Fighter Program ('the F-35 Program') would be somehow legally complicated. In our article we highlight some issues from legal perspective   apart from political discussions.