On the weekend, 12 Years a Slave won the Academy Award for Best Adapted Screenplay as well as Best Picture. There has been some controversy around the authorship of the screenplay. Apparently Steve McQueen believed at one point that he should have received a writer credit, John Ridley disagreed, and so Ridley ended up with the credit and therefore the award.
These kinds of things usually don't happen. The Writers' Guild of America has literally over 50 pages in its Collective Bargaining Agreement setting out the criteria for assigning credit and, if there's a dispute between writers, the arbitration method for settling it. So why didn't that happen here?
Believe it or not, the answer may be found in labor law.