Actor Kevin Costner has played courtroom dramas before -- you may remember his turn as New Orleans District Attorney Jim Garrison in Oliver Stone's "JFK."  Now Costner is in a real-life legal drama here in New Orleans, that has its origins in the 2010 Gulf oil disaster.

Costner is the defendant in a case brought by actor Stephen Baldwin.  Baldwin was an investor in Costner's company that makes machines built to clean up water after an oil spill, but he sold his stake shortly before Costner negotiated an $18 million deal with BP to use his company's machine as part of the cleanup effort.

Baldwin claims Costner should have told him he was on the verge of landing that deal before Baldwin sold his share for $1.4 million. He and another plaintiff are seeking $21 million in damages.

Costner has countersued, arguing Baldwin somehow managed to get $1.4 million "despite having invested no money in the company."

Both actors are expected to testify in the federal lawsuit.