Brad Pitt has joined the Los Angeles cast of a play based on the trial over the constitutionality of California's gay marriage ban, Proposition 8.

The 2010 trial, which was held in San Francisco, resulted in federal Judge Vaughn Walker, now retired, declaring the 2008 voter-approved amendment unconstitutional. A 3-judge appeals panel last month upheld Walker's ruling. Proponents of the ban have asked the court for a wider review.

Pitt will play Walker in the Los Angeles premiere of the play, simply titled 8 and penned by Milk scribe Dustin Lance Black.

The March 3 reading includes a bevy of Hollywood heavyweights, including George Clooney, Jamie Lee Curtis, Matt Bomer, Martin Sheen, Jane Lynch and George Takei, to name a few.

The American Foundation for Equal Rights (AFER), the group formed specifically to support the legal challenge, also announced that the reading will be streamed live on its YouTube channel starting Saturday at 7:30PM PST.

The Broadway premiere of 8 raised over $1 million for the right to win marriage equality.

(Related: Nearly 60 percent of California voters support gay marriage.)