People on probation do not have the same rights as people who haven't been convicted of anything.  In most states, probation violation can be charged on reasonable suspicion.  Here, the police officer's sworn statement was enough to support the charge, if your boyfriend's probation terms say he can't be drunk.Your boyfriend has the right to a hearing, and he has the right to have a lawyer with him at the hearing.  It's a very good idea.  One place you can find a professional is http://attorneypages.com