Law and actor Aaron Johnson are in negotiations to Play key characters in the movie though it is not clear who will play what, the Variety reported.
The movie is being directed by Joe Wright, who reunites with Knightley for the third time after the success of period flicks like 'Atonement' and 'Pride & Prejudice'.
Knightley will play the title role of Anna, a woman who is torn between a loveless marriage and her struggle to cope with her attraction to a soldier.
The story of love and guilt has been adapted by Tom Stoppard while Working Title's Tim Bevan is producing.
The novel, considered one of the most poignant Stories of love and guilt, has already been adapted many Times, including a 1997 Warner Bros pic starring Sophie Marceau and Sean Bean.
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