In short, it appears at this point that the Turkish case justifying the use of deadly force is, at best, weak. Nevertheless, NATO Secretary General Jens Stoltenberg said that NATO stands "in solidarity with Turkey."Gen. Dunlap's article, below, is a very good discussion of international law on self defense. Turkey is wrong on this and Erdogan is responsible for the needless death of the Russian pilot.
But Stoltenberg couldn't wait to drink Erdogan's bathwater. He knows the substance of the legal realities Duncan has laid out and even on just the facts of the case Turkey is lying like a rug. As one commenter points out, the Turkish fighters gave 10 warnings over a five-minute period while the Russian plane was, for the sake of argument, only over Turkey for 17 seconds.
 "Russians may have a strong case in Turkish shootdown." By Charles J. Dunlap Jr., The Hill, 11/25/15.