The budget is about $25m and the project will shoot in the second half of 2007. The film is set in the US and Africa. Casting will start next month.
Mark Wheaton wrote the script about a Washington lawyer out of his depth during a Nigerian oil corruption trial.
Johnson, who is also an actor, previously directed The Sentinel and SWAT as well as episodes of TV dramas The Wire, Sleeper Cell and The Shield.
The producers previously worked on 2005's Diameter Of The Bomb.
'The film is constructed as an entertaining, mainstream legal thriller, but it also tackles head on the very current issues of corruption and western involvement in oil -rich African states,' Townsley says. ' Clark is the perfect director to bring political edge to a commercial movie and we are delighted to have him on board.'