The White House says President Barack Obama's administration will appeal.
Several companies that ferry people and supplies and provide other services to offshore drilling rigs had asked U.S. District Judge Martin Feldman in New Orleans to overturn the moratorium.
The administration halted the approval of any new permits for deepwater drilling and suspended drilling at 33 exploratory wells in the Gulf.
Feldman says in his ruling that the Interior Department failed to provide adequate reasoning for the moratorium. He says it seems to assume that because one rig failed, all companies and rigs doing deepwater drilling pose an imminent danger.
