Jokes aside, I think the idea is that the law is simple to code, the proof that it holds is where the agent is responsible. This probably becomes less true though as you try to express more complicated laws.
Heh, it's like we all need to collectively read I, Robot yet again, and the myriad of SF books on the subjects. Black and white quickly dithers to grey.
The point of those books is that robots can be perfectly rational, and for a useful robot we would expect them to be.
What they aren't is moral, because of the orthogonality principle: you can't use facts and logic to discover correct moral beliefs. Morality is about values, goals, and the definition of "good". They must be provided to the robot by its creator, and those are things that are very hard to precisely describe in a way that is fully consistent with the speaker's intent in all possible scenarios, and agreeable by all other people.
