LAST WEEKEND Hugh Hewitt, director of the Nixon Presidential Library in Yorba Linda, Calif., allowed in response to a journalist's question that it would be "a taint to let the premises be used indiscriminately by groups who oppose everything he {Mr. Nixon} has worked for." Questioned further, he said, "I don't think we'd ever open the doors to" Washington Post reporter Bob Woodward, since "he's not a responsible journalist." Inquiries came quickly from Nixon scholars and others, who pointed out that no reputable research library screens access to researchers on the basis of possible disagreement with their conclusions. Mr. Hewitt then said he'd been mistaken and that the library's not-yet-assembled archives would be open to all comers.

It's the sort of problem that has cropped up before in the establishment of other presidential libraries, those hybrid institutions created with privately raised funds but operated by the federal government for a public purpose. Those who have committed funds and time to the memorializing of a president, whether a popular one or an unpopular one, tend to want him to appear in a favorable, even worshipful light. The public interest served by government stewardship of these museums, though, is in comprehensiveness, scholarly objectivity and -- it goes without saying -- full public access.

The contrast between these aims becomes sharper when the president in question resigned in disgrace. Partly for this reason, the Nixon library, in contrast to those of most ex-presidents, is a wholly private and privately funded endeavor. The government has no oversight or control, and it holds the vast bulk of the Nixon presidential papers elsewhere, in the National Archives and other places, where most are in fact open to the public. (Owing to continuing legal struggles over some of this material, the Yorba Linda facility will offer only copies of some documents from the Watergate years.)

The opening of this separate California library, in the town where Mr. Nixon was born, has been characterized by supporters as a step in its subject's full rehabilitation. Any suspicion that the library might be less than a reputable scholarly establishment would surely set back that lofty ambition.