Bulgaria, the European Union's poorest member, is still blighted by corruption and organised crime more than 20 years after the fall of communism, and is under pressure from Brussels to tackle the problem.
Zlatomir Ivanov, 44, was shot four times in his legs, an arm and his stomach as he was entering the court for an appeal against his eight-year jail sentence, police said. Ivanov and his bodyguard, who was also wounded, were taken to hospital, where Ivanov was due to undergo surgery.
Local media say that Ivanov is a former member of a special police force known as The Berets.
Because of health problems, he had been allowed to remain under house arrest while awaiting his appeal.
Prime Minister Boiko Borisov said: "The site gives easy access for a shooting. If he had been in custody, he would have had protection."
Mr Borisov's ruling GERB party swept to power promising to put an end to a climate of impunity.