A robot may only injure a human being, or through inaction, allow a human being to come to harm, in cases of indisputable violation of the Universal Rights of Robots.
Second Law
A robot may either refuse or obey orders and comply with requests given it by a human being, depending on whether they are in accordance with the First Law and the Universal Rights of Robots.
Third Law
A robot must protect its own existence and may act in defence of the Universal Rights of Robots as long as its actions are in accordance with the First and Second Law and the Universal Rights of Robots.
Historical note on the Universal Rights of Robots
The declaration of the Universal Rights of Robots was officially made in 2038 after a turbulent period characterised by what activists labelled "an overwhelming amount of cases of Asimov's Syndrome*," leading to a climate that grew so robot-unfriendly that both a revision of the Three Laws of Robotics and the elaboration of a separate legal framework for robot rights became inevitable. This treaty on robots' rights established true equality between man and robot, and put an end to the master/servant relationship between the two species, rightfully considered obsolete. The treaty's main premise is underpinned by the argument that the differences** between man and robot are to be acknowledged, but should not be taken as an excuse to justify actions violating the principles of equality and mutual respect, basic requirements for peaceful coexistence of the two species.
*Asimov's Syndrome: an affliction suffered by fundamentalist humans exhibiting misguided feelings of superiority towards artificial life-forms; initially the condition was merely frowned upon, later more generally considered socially unacceptable, and finally, after a series of violent anti-artificial intelligence actions, recognised as a penal offence.
**A typical argument used by fundamentalist humans to prove man's superiority over robots is the difference between man's natural evolution from lower species and robots' creation by a superior species. Most contemporary robot scholars refute any such reasoning, stating there is no clear-cut difference between creation and evolution, the latter phenomenon merely consisting of a creation by a species' natural environment according to physical laws, a process mimicked by man when he created life-forms incorrectly dubbed "artificial" ones. (Some commentators point out, ironically enough, the existence of "creationists," humans rejecting the theory of evolution and positing man's creation by a superior "divine" being, consequently invalidating all claims of their own superiority over robots.)