I am not a lawyer, but it looks there could be a major issue if, on January 11 2007, George Michael is convicted of being unfit to drive through use of drugs. What would that issue be? Well, it looks like being convicted of this particular offence may have the effect of automatically ensuring refusal of visas for the United States. This would mean no US Tour.
(Update: It seems that being found unfit to drive through use of drugs, where no-one was injured, have historically not been considered serious enough to make someone inadmissible to the US. So, it there could be a good chance everything would be OK as far as the US tour.)