Marvin Norwood and Louie Sanchez -- already facing assault and mayhem charges in the March 31, 2011, incident -- have also been charged with weapons violations, the Los Angeles Times reported Tuesday.
Each was accused of being felons in possession of firearms in a 14-page indictment revealed by federal authorities during a Tuesday pretrial hearing.
Prosecutors contend Norwood and Sanchez of attacked Bryan Stow of Santa Cruz, Calif., in the stadium parking lot after the Opening Day game between the Giants and Los Angeles Dodgers.
Stow was wearing a Giants jersey when he was assaulted, they say.
The suspects stand accused of possessing two semiautomatic rifles, a semiautomatic shotgun, a semiautomatic pistol and a .357-caliber revolver, which were recovered during a search of Norwood's home, the newspaper reported.
Stow suffered a serious head injury in the alleged assault and was moved from a San Francisco hospital to a rehab center late last year.