Ulemek, aka Legija, was sentenced by the Special Court Against Organised Crime in Belgrade on Monday.
The same verdict sentenced JSO members Branko Bercek, Dusko Maricic and Nenad Bujosevic also to 40 years in jail, while Leonid Milivojevic and Nenad Ilic were given 15 years' sentences.
A former Serbian Interior Ministry State Security Department chief, Radomir Markovic, was sentenced to 15 years in jail for helping the perpetrators of said crimes, while Milorad Bracanovic, ex-chief of the JSO Counterintelligence and Security Department, was sentenced to four years' imprisonment for failing to prevent and report the crimes.
Under the ruling, Bercek, Maricic, Bujosevic, Milivojevic and Ilic will also have to return 55,000 euros which they received from Ulemek as an award for killing Stambolic and attempting to kill Draskovic.
The Stambolic murder and Draskovic assassination attempt were solved after the March 2003 assassination of Serbian Prime Minister Zoran Djindjic, when Stambolic's body was discovered in a quicklime ditch on Mount Fruska Gora. The site was shown to the police by JSO member Nenad Sare.
Stambolic was kidnapped and murdered on 25 August 2000, while the attempt at Draskovic's life was made on 15 June 2000.
Late last month, the Belgrade District Court sentenced Ulemek, Bercek, Maricic, Bujosevic, Milivojevic and Ilic to 15 years in jail for another attempt at Draskovic's life, in 1999, when four members of his Serbian Renewal Movement, the then strongest opposition party in Serbia, were killed.
Ulemek is also on trial before the Special Court Against Organised Crime for the Djindjic assassination as well as for a series of kidnappings, murders and other grave crimes committed by the so-called Zemun Clan.