The governor rejected the state parole board recommendation in January that said Davis, 67, is ready to be released four decades after the two murders.
The governor acknowledged that Davis has made credible accomplishments during his incarceration, but Schwarzenegger said the murders were "especially heinous" and Davis has repeatedly minimized his involvement.
While in prison, Davis earned a master's degree in religion and a doctorate in philosophy of religion. He also got married and fathered a daughter.
Schwarzenegger said in a letter made public Monday that he questions whether Davis is still too willing to follow others' direction, saying he finds it troubling Davis said he would be subservient to his wife if he's released.
Davis' attorney says he will file a lawsuit in Los Angeles County Superior Court to reverse the governor's decision.
He said Schwarzenegger has no valid grounds to reject the recommendations of the parole board.