According to González Iñárritu, Arriaga holds an "unjustified obsession with claiming the sole authorship of a film." He goes on to tell his ex-partner: "You were not -- and you have never allowed yourself to feel -- part of this team," and "Your declarations are a sad and very reductive end to this wonderful collective process that we have lived and are now celebrating."
It almost sounds like the director is trying to tell the screenwriter to shut up, grin and bear it (instead of fighting for ownership of his ideas). The letter is signed not only by González Iñárritu, but also by Perros star Gael García Bernal, Oscar-nominee Adriana Barraza, composer Gustavo Santaolalla and cinematographer Rodrigo Prieto. Ouch. He might have also wished the writer "luck in your future movies," but the damage has already been done to Arriaga's reputation. Then again, he's the only one of the duo to have a successful award-winner outside of the partnership, so time will tell.