Doherty was escorted to a police station near the court
Rock singer Pete Doherty was arrested in court moments after being spared a jail term for admitting driving home drunk from a gig in Gloucester.
The 30-year-old Babyshambles frontman was fined £2,050 and banned from driving for 18 months after admitting careless and drink-driving.
He was then escorted from Gloucester Crown Court to a nearby police station.
Police confirmed he had been arrested on suspicion of possessing a controlled drug but would not reveal which type.
Doherty was stopped in the early hours of 11 June when police saw a car being driven erratically in Gloucester.
He admitted to drink-driving that night, having given a reading of 50mg of alcohol per 100ml of breath.
Prosecutors said Doherty had stopped the Mercedes and swapped seats with passenger Daisy Whitbread in an apparent attempt to avoid punishment.
The singer was disqualified from driving in 2007 and had not renewed his licence, the court heard.
Officers also found one wrap of heroin in the car, worth up to £35, and what was described as "home-made crack pipe" on the driver's seat.
A search of Doherty's country home in Durley, near Marlborough in Wiltshire, uncovered a further 15 wraps worth around £350.
Sarah Regan, prosecuting, said: "Mr Doherty was pulled from the door and arrested.
"It was noted that he was extremely unsteady on his feet, his eyes were glazed and he smelt very strongly of alcohol, causing the officer to form the view he was drunk."
Doherty had earlier admitted to two counts of drugs possession, driving without a licence and without insurance.
A Gloucestershire Constabulary spokeswoman said: "A 30-year-old Wiltshire man has been arrested on suspicion of being in possession of a controlled substance.
"He is currently assisting police with their enquiries."