Apart from that excellent trio of actors, the outstanding supporting cast also features Jessica Chastain, Gary Oldman, Mia Wasikowska, Guy Pearce, Noah Taylor and up and comer Dane DeHaan (the "evil" kid in "Chronicle").
There's also an official synopsis via The Weinstein Company:
Gangster meets Western in LAWLESS, the true story of the freewheelin’ Bondurant brothers, bootlegging siblings taking the law into their own hands. This is the story of the rural hard-men that created the big city gangsters. Brazen and fearless, these young rebel brothers helped build the American Dream in this exuberant tale of what was to become crime’s first major gold rush. The youngest brother, JACK (Shia LaBeouf), fancies himself the next Al Capone; he dreams of sharp suits, guns, girls and fast cars, no matter the cost. Ambitious and impulsive, he takes the family’s small-scale moonshining operation to the big leagues, to impress the gorgeous but off-limits Amish girl, BERTHA (Mia Wasikowska). The middle brother, HOWARD (Jason Clarke), is the brawling muscle – loyal but reckless – never one to turn down a taste of white lightning. And eldest brother, FORREST (Tom Hardy), reluctantly accepts the changing times with grace and grit, leading the family with strength of character and silent determination against the beginnings of corporate greed. An enigmatic and stunning MAGGIE (Jessica Chastain) comes to town with a hidden past, igniting his passion and almost saving him in the process. As the Bondurants’ legend grows, so too does the danger, and it’s not long before the brothers must face the consequences of their transgressions, or rewrite the myth and the law themselves.
Due August 31st, Harvey Weinstein himself promises we'll see the film a few days earlier when the 2012 Venice Film Festival kicks off. The hope for TWC is that this summer's "The Dark Knight Rises" turns the much-in-demand Hardy into a bonafide star.