Lawyers for Richard M. Nixon’s estate have accused the Justice Department of filing a “melodramatic” appeal that ignores provisions of a 1974 law requiring the return of private conversations on his White House tapes to Nixon or his heirs.

At issue are segments on the original tapes, totaling about 820 hours but intermingled with historically important material as well as portions dealing with President Nixon’s “abuses of power” that Congress decreed should be made public. U.S. District Judge Norma Holloway Johnson last spring ordered the return “forthwith” of the private portions on the original tapes and any copies.

Seeking summary affirmance of Johnson’s ruling in the U.S. appeals court here, Nixon lawyer Scott L. Nelson said the law and past court rulings make plain that the government cannot retain private materials on the tapes and that the Nixon estate is entitled to “sole custody and use” of them.

Even if the necessary editing results in some damage to the original tapes, Nelson said, the National Archives will have enhanced copies that government experts acknowledge can be safely edited “without damaging them at all, and without the loss of a single second of the nonprivate conversations.”

The Justice Department argued in an appeal filed June 23 that the 1974 law governing the tapes obliges the government to make sure the originals not be “lost or destroyed.” “On this 25th anniversary of Watergate,” the Justice lawyers said, “the lessons of history should not lightly be left as cuttings on the editing room floor.”

The Nixon reply dismissed this as a “melodramatic assertion.” Nelson said the 1974 law explicitly states that none of its other provisions are to apply “to any tape recordings or other materials” designated by government archivists to be returned to Nixon.

Nelson also disputed the government’s claim that editing the original tapes would be “tantamount to destroying them” because of their age and fragility. The National Archives, he pointed out, does not allow the originals to be played, and its experts say they soon will deteriorate “to the point of uselessness.”

As a result, the Nixon lawyer said, “it is hard to see what will have been lost to history -- other than the private conversations, which the government says it will never allow anyone to listen to.”

The dispute is an offshoot of a lawsuit filed by historian Stanley Kutler and the advocacy group, Public Citizen, to obtain access to the historically significant segments.