What right will we have to criticize Putin if he kills Ukrainian president Zelenskyy?

From a legal standpoint, the US has illegally killed the leader of Iran in an illegal war which our leaders are not even criticizing. They are just accepting that the US takes out a leader they do not like, thereby destabilizing a nation of 93 million people.

International law does not allow this, but if we do not uphold international law, what boundaries do we have left to limit dictators like Putin?

@randahl International law is a set of rules and regulations created by great powers and works only if it's enforced by great powers. The problem starts when great powers leaders are dictators, then international law exist on paper, but no one to enforce. This is the time we are living in.