I mean it would be enough to tell it to "Not cheat" or "Don't engage in unethical behaviour" or "Play by the rules". I think LLMs understand very well what you mean with these broad categories.
Very specific rules that minimize the use of negations is more applicable. This is also kind of why chain of thought in LLMs can be useful, in that you can more explicitly see the steps and take note when negation demands aren't being as helpful as you would think.
Not just negation demands, but also generally other tricks we use for thinking and communication shorthands. "Unethical behavior" here for example, we know what that means since the context is clear, but to LLMs that context can be unclear in which the unethical behavior can mean well... anything.
Thou shall not Cheat
Thou shall not Defraud
Thou shall not Deceive
Thou shall not Trick
Thou shall not Swindle
Thou shall not Scam
Thou shall not Con
Thou shall not Dupe
Thou shall not Hoodwink
Thou shall not Mislead
Thou shall not Bamboozle
Thou shall not ...
Not just negation demands, but also generally other tricks we use for thinking and communication shorthands. "Unethical behavior" here for example, we know what that means since the context is clear, but to LLMs that context can be unclear in which the unethical behavior can mean well... anything.