The Justice Bloc was the most powerful voting bloc of Vault 11 at the time preceding its decline, whose goal alongside the other blocs was to heavily influence the votes of fellow vault dwellers in overseer elections.
Prior to the final election, members of this group led by Roy Gottlieb, extorted sexual favors from fellow resident Katherine Stone. They threatened to nominate her husband, Nathan Stone, as overseer should she resist. Due to their overwhelming influence as a voting bloc, this would essentially be a death sentence for her husband, and she capitulated to their demands. Afterward, the Justice Bloc members betrayed Katherine, nominating her husband regardless of her submission to their whims.
Out of desperation, despair, and indignation, Katherine enacted a plan of retribution, subsequently murdering members of the Justice Bloc one by one. This worked for Katherine in two ways, as she had not only set the stage for reprisal but also would be a clear choice for the next overseer in place of her husband, effectively saving his life. Katherine's plan succeeded on both accounts, and after the murder of Justice Bloc members, she was elected as the next vault overseer.
Katherine Stone's first act as overseer, "Overseer Order 745," dissolved the election process entirely and decreed that moving forward, the position of overseer would be chosen at random using the vault's computer systems. The Justice Bloc, aghast at the thought of losing their control and influence over the vault population, decided to stage an armed coup. The fighting that ensued killed nearly all of the remaining vault dwellers. Of the survivors, as told by an audio log, four committed suicide with the last survivor's fate unknown.
The Justice Bloc is only mentioned in Fallout: New Vegas.