Allen - Prolegomena to Any Future Moral Agent places a lot of emphasis on figuring out of a machine can be truly moral, in various metaphysical senses like "has the capacity to disobey the law, but doesn't" and "deliberates in a certain way". Not only is it possible that these are meaningless, but in a superintelligence the metaphysical implications should really take second-place to the not-getting-turned-into-paperclips implications.

He proposes a moral Turing Test, where we call a machine moral if it can answer moral questions indistinguishably from a human. But Clippy would also pass this test, if a consequence of passing was that the humans lowered their guard/let him out of the box. In fact, every unfriendly superintelligence with a basic knowledge of human culture and a motive would pass.

Utilitarianism considered difficult to implement because it's computationally impossible to predict all consequences. Given that any AI worth its salt would have a module for predicting the consequences of its actions anyway, and that the potential danger of the AI is directly related to how good this module is, that seems like a non-problem. It wouldn't be perfect, but it would do better than humans, at least.

Deontology, same problem as the last one. Virtue ethics seems problematic depending on the AI's motivation - if it were motivated to turn the universe to paperclips, would it be completely honest about it, kill humans quickly and painlessly and with a flowery apology, and declare itself to have exercised the virtues of honesty, compassion, and politeness? Evolution would give us something at best as moral as humans and probably worse - see the Sequence post about the tanks in cloudy weather.

Still not impressed.