For one, if the rules are called out by the T after the LR has been accepted by a CT, they are not required to be followed by the CT. Just clarifying that.
However, if the rules are called out by the T before the LR is accepted, and the CT agrees and accepts, that CT MUST follow the rules stated by the T and if he doesn't it is considered cheating. For example, a T says you cannot right click in a knife fight, and the CT right clicks and the T dies, that's a freekill.