When I first started playing with a group of completely new players, one of the first things I did was to explain the alignments as best I could at the time. When describing Chaotic Neutral, my exact words were, "A chaotic neutral character will do whatever he wants to do, so long as there is a reason that is justifiable to at least him behind doing so."
Well, recently, I'm beginning to think that that explanation is not exactly accurate, or at least not perfectly clear.
To explain, through every game I have played with this group, I have regretted each and every time I allowed a player to play a chaotic neutral character. The exact same thing will happen, no matter how many times I explain why it shouldn't. Said character will, for no reason I can fathom other than because his player (and by extension the character itself) wants to. Anything from using a squirrel to test out a new spell, to burning down the local pub to stop the flow of polluted beer, to openly mocking authority figures until nothing short of character death is put on the table, and even then only because I made the desire for self-preservation a required character trait. This is not to say that they do this because they prefer to, or that it's simply a style of play that they find more fun. We've played campaigns where I banned chaotic-neutral alignment, and everyone enjoyed themselves without this being an issue. It's simply that, whenever this issue comes up, I'll point it out to them and they'll reply with some variant of, 'I'm a chaotic character, and I'm being chaotic. Why is that wrong?" I don't have an answer to that.
So, what's a better way to describe a chaotic neutral character? How do I explain to this group that, even if the alignment is 'chaotic,' that doesn't mean they have to play either chaotic-stupid, or insane?