Law enforcement sources confirm ... Steve-O was stopped by customs when he got off an airplane at Calgary International Airport, when officials noticed there was an outstanding warrant out for his arrest.
The warrant was issued back in 2003 -- for an incident in which Steve-O allegedly attacked somebody with an unknown object. So far, the identity of the victim is not yet public.
Steve-O was placed behind bars for a short while -- before going in front of a judge. He was soon released on $10,000 bail which the actor had to pay IN CASH (It pays to be a Jackass I guess). Steve-O is due back in court in May.