Three Laws of Robotics
From Halopedia, the Halo wiki
The laws were created by science fiction author Isaac Asimov, with the first law first mentioned in the 1941-story Liar!. Fleshed out more extensively in later series, these laws have also been adopted by other science fiction authors, albeit sometimes in an altered form, and has been considered a good model on which to base future artificial intelligence research.
United Nations Space Command "smart" AIs are able to ignore at least the first law at will while fully functional, and given their military usage are often required to ignore this law, though at lower-capacity states their adherence is compulsory. Whether "dumb" AIs are able to ignore these laws is unknown.
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