You are correct in that this (and many other related articles) are not directly saying what Iran did is wrong... however, I feel the general tone and overall implication is that Iran have "taken" a drone that doesn't belong to them, and clearly are not about to give it back.

So as you say, "law" doesn't really apply, it's more of a moral decision as to whether a country should spy on another country. We can clearly see the outcome of that decision here.