SEC administrative law judge Brenda P Murray exonerated SEC director of enforcement Linda Thomsen, assistant director of enforcement Mark Kreitman and SEC attorney Gary Aguirre over their handling of the probe into Pequot Capital Management, HedgeCo stated.
The ruling goes against earlier findings from the regulator's inspector general, H David Kotz, that the conduct of the investigation raised "serious questions about the impartiality and fairness".
Previous reports from the Associated Press said an SEC lawyer who worked on the case and has since been fired from the agency had accused officials of "political interference". No action was taken against Pequot and the hedge fund denies any wrongdoing.
In a statement, Mr Kotz said: "We were surprised and disappointed by the administrative judge's decisions ...We also have serious concerns about the process utilized in arriving at these decisions."
Ms Murray also cleared the SEC over a separate investigation into Bear Stearns, which collapsed earlier this year, the AP noted.