As a general rule, I tend to look at the morality of remote gadgets by asking if it would be OK if a human did it first hand. CCTVs are acceptable if it would be reasonable to have a cop or security guard standing there looking; otherwise, no.

In this case, it ought to be self evident that if you're not allowed to send a soldier into Ruritania to shoot someone your government dislikes (or someone who happens to have the same name as the target, or lives in the house next to his,) then you're not allowed to send a remote controlled bomb. I am at a loss to imagine who in the State Department decided that international law doesn't apply to 21st Century doodlebugs. I'm afraid it is much more likely that the reasoning behind it was "because we can."