It's called "committing a felony involving moral turpitude" and it's in a clause of the Warlock's contract.
Here's what's directly from the letter to Sheen's lawyer:
"There is ample evidence supporting Warner Bros. reasonable good faith opinion that Mr. Sheen has committed felony offenses involving moral turpitude (including but not limited to furnishing of cocaine to others as part of the self-destructive lifestyle he has described publicly) that have 'interfere[d] with his ability to fully and completely render all material services required' under the agreement."
The letter also described specific instances of worry:
"Your client has been engaged in dangerously self-destructive conduct and appears to be very ill."
[It] goes on to describe Charlie's hijinks, including trashing the Plaza Hotel in NYC, coke binges, on-set failures because of drug fatigue, and diatribes against "Two and a Half Men" creator Chuck Lorre.
Not good, Sheen.
We guarantee that Charlie is just getting started in the legal department, but this seems like a pretty legit reason to us for him to be fired. We don't really see a positive outcome for him on this one, as far as going back to the show is concerned.
More on this as details come in.
[Image via WENN.]