Is there a international law that decides who is a terrorist, and based on the acts committed in Ukraine, can Vladimir Putin be judged as a terrorist?
In recent decades, the term 'terrorist' has been so over-used as to become meaningless, unless an exact context is given.
- Criminal acts intended or calculated to provoke a state of terror in the general public, a group of persons or particular persons for political purposes are [...]
Note that the UNGA talks about criminal acts. Under international law, war is not always a crime. Also, the individuals engaged in war are not held to the normal criminal law standards even if starting the war was a crime. A soldier who shoots at an enemy soldier does not have to prove self-defense under criminal law standards.
International law has various conventions and customs regarding starting wars (jus ad bellum) and fighting wars (jus in bello).
- The crime of aggression is unlawfully starting a war. It is not commonly called terrorism or state terrorism. President Putin may or may not be guilty of this, he has not been tried and found guilty. (I have a firm opinion on his guilt, but I'm not a competent court of law.)
- War crimes are various acts during a war, regardless of whether the war itself was lawful or not. They are often called terrorist acts, but this is an oversimplification for propoaganda purposes. Both President Putin and some of his subordinates may or may not be guilty of this. Ukrainian courts have sentenced Russian soldiers for war crimes, just as Russian courts have sentenced Ukrainians. (I believe that soldiers on both sides committed war crimes, with the preponderance being Russian crimes, and also that both Ukrainian and Russian trials are influenced by political considerations. I believe that Russia is ordering war crimes, while Ukraine is failing to prevent crimes by their troops.)