WASHINGTON — A federal appeals court held Friday that the Central Intelligence Agency must disclose, at least to a judge, a description of its records on drone strikes in response to a Freedom of Information Act lawsuit filed by the American Civil Liberties Union.

The 19-page opinion by Judge Merrick B. Garland rejected an effort by the Obama administration to keep secret any aspect of the C.I.A.’s interest in the use of drone strikes to kill terrorism suspects abroad.

It does not necessarily mean the contents of any of those records will ever be made public, and it stopped short of ordering the government to acknowledge publicly that the C.I.A. actually uses drones to carry out “targeted killings” against specific terrorism suspects or groups of unknown people who appear to be militants in places like tribal Pakistan. The Obama administration continues to treat that fact as a classified secret, though it has been widely reported.

But the ruling was a chink in that stone wall. Judge Garland, citing the C.I.A. role in analyzing intelligence, as well as public remarks by a former director and other top officials about what they asserted was the precision and minimal civilian casualties caused by drone strikes, said it was a step too far to ask the judicial branch to give its “imprimatur to a fiction of deniability that no reasonable person would regard as plausible.”

He wrote that “as it is now clear that the agency does have an interest in drone strikes, it beggars belief that it does not also have documents relating to the subject.”

The C.I.A., in urging a District Court judge to dismiss the lawsuit, had argued that it should not be required to produce even an index of the relevant documents in its possession — a normal step in such litigation — because it would harm national security even to confirm or deny whether it had an “interest” in such operations.

The District Court judge, Rosemary Collyer, accepted that argument and rejected the A.C.L.U.’s case, and the ruling on Friday sends the case back to her. It remains to be seen how detailed and public she will require the agency to be now that it must at least describe its records.