Lassi and Kareem were found guilty of using the banned drug cannabis to enhance performances during the 2002 Asian Games.
Shakeel Durani, a spokesperson for the Pakistan Boxing Federation said, "the Pakistan Sports Board has informed us that the two boxers have been banned for six months, which is bad news for us".
"But their absence will definitely hit our chances in the Doha Asian Games next month," he added.
"We had kept them in the Asian Games squad in the hope that they would be cleared but now they have been banned we will replace them with other boxers," said Durani.
The 26-year-old Lassi also won a silver medal in the Commonwealth Games in Melbourne this year.
The SAF Games committee said their gold medals have been withdrawn.