WHEN it comes to providing testimony that could determine guilt or innocence, presidents, like all citizens, should do their duty. President Reagan and president-to-be Bush should respond to the subpoenas served by Oliver North's lawyers. That doesn't mean, however, that the man who occupies the nation's highest office should spend hours in court under cross-examination. The president's testimony can be delivered through written deposition, or even videotape. This would accord with historical precedent. Presidents from Thomas Jefferson onward have submitted evidence.
George Bush will be in the White House when Mr. North's trial is scheduled to start on Jan. 31. Thus he'll be in the position of invoking the traditional argument of executive privilege against appearing in court - an argument that should be honored.
Mr. Reagan will have lost his claim to that argument. As constitutional expert Lawrence Tribe has noted, it's the office of president, not the man who may once have held it, that is protected by executive privilege.
But taped or written evidence may suffice from Reagan too. Certainly the former president will want to cooperate. He has resisted substantial pressure to pardon North, and some see the current subpoenas as another version of that pressure.
Reagan has insisted that the legal process should run its course on Iran-Contra. We agree.