A man accused of uploading a copy of the biopic film Walk the Line has been charged with copyright infringement.
Witherspoon and Phoenix are both nominated for Oscars
Luis Ochoa, 25, of Corona, California, faces up to a year in jail and a fine, if found guilty.
Prosecutors say Mr Ochoa uploaded a "screener" version of the Oscar- nominated film, which was intended for an Academy voter.
Mr Ochoa was arrested after the Motion Picture Association of America (MPAA) set up a web sting, they added.
It was set up after a web-user contacted the MPAA and told them Mr Ochoa allegedly mentioned in a chat room that he wanted to put the film online.
The MPAA responded with the fake film-swapping website, where Mr Ochoa allegedly uploaded the film on 21 December.
Assistant US Attorney Brian Hoffstadt said a digital watermark showed the copy of Johnny Cash biopic Mr Ochoa is accused of posting on the internet was a "screener" copy sent to an Academy voter.
He added it had allegedly been taken before it reached the intended recipient.
Walk the Line, starring Joaquin Phoenix and Reese Witherspoon is nominated for five Oscars, including best actor and actress.
The awards will be handed out in Los Angeles ceremony on 5 March.