TMZ.Com tells us that Charlie Sheen will plead not guilty today in Aspen — weather permitting — to felony menacing and two misdemeanors, but the judge could ask a question that could land Charlie in jail.

Charlie is currently out on bail for the Christmas Day incident involving his wife, Brooke Mueller. One of the conditions of bail — Charlie can’t consume alcohol or use drugs.

Our sources say Charlie has fallen off the wagon since his arrest … which is why he’s currently in rehab. If the judge asks Charlie about rehab during Monday’s arraignment and whether alcohol and/or drugs drove him there, Charlie is in a no-win situation.

If he tells the judge he consumed alcohol or used drugs, his bail can be revoked and he could be thrown in jail. If he tells the judge he did not use alcohol or drugs, he could face a perjury charge.

Technically, all Charlie has to do is say two words — not guilty. The judge isn’t required to ask about anything. But if he does … all bets are off.

Charlie is scheduled to fly out this AM from L.A. to Aspen. Flights were canceled last night because of weather.

TMZ.Com tells us that Charlie Sheen arrived at a rehab facility in the L.A. County area at 8 PM PT Tuesday … TMZ has learned.

Sheen’s rep said earlier in the day the “Two and a Half Men” star was already in rehab.

But sources tell TMZ there were several delays, primarily because Sheen’s team wanted to make sure there were no legal ramifications resulting from Charlie’s move.

Sources tell us Charlie had been “slipping” and that’s why he decided to go into rehab.

TMZ contacted Arnold Mordkin, the prosecutor in Charlie’s criminal case in Aspen, to find out if he was contacted by Charlie’s lawyers and whether he gave any assurance he would not try and revoke Charlie’s bail. Under the terms of bail, Charlie cannot take drugs or drink alcohol.

Mordkin sounded surprised but said he could not comment one way or the other.

As we first reported, Charlie is not in the same rehab facility as his wife, Brooke Mueller.

As for their kids, they were sleeping soundly Tuesday night. Charlie’s mom was at the house and Martin Sheen joined her after performing his play in L.A.