He also said, "There is no evidence that wounded troops care about the sexual orientation of the flight nurse or medical technician tending to their wounds."
Leighton hailed Witt for her role "in a long-term, highly charged civil rights movement," telling her, "Today, you have won a victory in that struggle."
Witt, 46, of Spokane, said she was "just so thrilled I have the chance to do what I wanted to do all along: That's return to my unit."
Witt joined the Air Force in 1987. She was suspended in 2004 under "don't ask, don't tell" after her commanders learned she was in a lesbian relationship with a civilian. She was discharged in 2007.
Her fight to be reinstated has attracted national attention as part of the broader battle about whether gays and lesbians will be allowed to serve openly in the military.
Earlier this week - just hours after the six-day trial in Witt's lawsuit concluded - Republicans in the Senate blocked efforts to push through a repeal of the 1993 policy, which bars the military from asking about the sexual orientation of service members, but allows the discharge of those who acknowledge being gay or are discovered engaging in homosexual activity.
Opponents of the policy have waged a separate legal effort in federal courts. Earlier this month, they won a victory when a federal judge in California ruled that the policy was unconstitutional. The Justice Department is trying to prevent that judge from issuing an injunction that would halt the ban on openly gay troops.
Defense Secretary Robert M. Gates has said he favors repealing "don't ask, don't tell," and his department has set a December deadline to complete a study of the effects of lifting the ban.
The Justice Department did not immediately comment on Leighton's ruling, but James Lobsenz, Witt's attorney, said he expected an appeal.
Witt was represented by the American Civil Liberties Union of Washington.
