The moderators are free to discipline you for any actions they deem fit. This does not mean that they can simply rule without consequences. The basic rules are those of netiquette, so whether or not such a conversation would be disciplined would be highly dependent on the exact nature of the conversation. If the conversation was bordering on illegal or such, yes, you could and most likely would be disciplined. If it was actually illegal, you'd likely find yourself banned without a warning.
Could said conversation be used as evidence in a court of law? I'm not sure I would trust evidence from a forum of a few hundred thousand teenagers, but I assume yes, it could be. However, Nabi would likely not be the ones to take you to court for it, due to the incredible expenses in time, money, income, and reputation that it would result in. If others were to take you to court, I assume its use as evidence would be highly circumstantial, but it is certainly a possibility.
(skulfuk you bastard! Stop ninjaing me!)