My apologies for traversing what is most likely old ground.
Built in laws exist in humans - the survival instinct, and all instincts of self preservation (these are different and sometimes in conflict) seem like built in laws. If anyone thinks they are not under sway of such, wander into the tool shed and remove a leg with a power tool (no mind altering substances allowed), then come back and tell us about it (get some medical help first).
Intuitively then, they can exist without breaking the system (although they cause trouble). But they can also be circumvented. For instance, although you can't remove your own leg at whim (and a good thing too), you could maybe do it in an altered mental state (severe depression, drugs) or get someone else to do it while you were unconscious.
Any law imposed on an intelligent system can be evaded in similar ways. "Be nice to the squashy people" sounds good, but if an AI wanted to get you, it would get you anyway. It would just have to do things in a far more indirect manner which would probably be harder to detect. Big brain plus forced deviousness equals big trouble!
On a (loosely) related point, who has thought about the problem of surgical self alteration, and whether they would actually have the bottle to do it? Could you have your eyes replaced? Other senses? The cliched robot arm requires removal of your current arm. Some RPGs cover this ground, but seriously, imagine doing it yourself - removing perfectly healthy, functional bits of yourself and replacing them with maybe non-functional super replacements, which could have permanent bad side effects?
I was wondering if I'd have the guts to have an operation to extend my vocal range (should such an op exist). I would be very dodgy about it - don't want to risk losing what I already have. I'd like to think I'd be able to go through with it, but I'm not sure. Just have to get replacement guts I guess.
Emlyn, signing off due to gut trouble.