The Federal Court in the Southern District of Texas upheld the board's legal authority to investigate the blowout and explosion at the Deepwater Horizon oil rig in the Gulf of Mexico in 2010.
The CSB said Transocean, which leased the rig to BP, raised a number of legal arguments challenging its authority to access information related to the disaster.
The 2010 incident left 11 rig workers dead and resulted in the worst offshore oil spill of its kind in the history of the oil industry.
The CSB said the court found that Transocean raised no substantial challenge other than to claim the board exceeded its statutory authority.
"This ruling greatly supports the CSB's ongoing investigation and will enable CSB investigators to access critical information that might have otherwise been unavailable," the board said in a statement.
The CSB said it's taking a "broad look" at the 2010 spill. It's examining regulating agencies as well as safety controls, corporate governance and human factors.
Transocean has pleaded guilty to a misdemeanor environmental charge and agreed to pay $1.4 billion in civil and criminal penalties. A separate trial is under way in a New Orleans court involving BP, Transocean and Halliburton.