AS IF HE didn't have enough to do already, Iran-contra special prosecutor Lawrence Walsh is now involved in litigation with a lawyer who was once a member of his own staff. The subject of the lawsuit is a book written by the attorney, Jeffrey Toobin, and Mr. Walsh's strong objections to its publication. Mr. Toobin, now an assistant U.S. attorney in Brooklyn, was only 26 when he was assigned to the Iran-contra team, and according to his publisher, he has produced a vivid insider's account of the investigation and the prosecutions that followed. Mr. Walsh claims the book breaches a confidentiality agreement Mr. Toobin had signed and has asked the Justice Department to consider criminally prosecuting the author for divulging privileged grand jury material.

Mr. Toobin says he has scrupulously complied with the confidentiality agreement and has for 18 months been submitting material to Mr. Walsh for clearance. Both the Justice Department and the CIA have reviewed the book and voiced no objection to publication, but the special prosecutor has refused to give his assent. Frustrated by the delay but fearing that he will be prosecuted, sued, fired and/or reprimanded by the bar association if he goes ahead without Mr. Walsh's approval, Mr. Toobin has gone to court in New York seeking a ruling that he has not violated the grand jury secrecy rule or any other obligation he undertook in connection with his Iran-contra work. U.S. District Court Judge John Keenan will review all the documents and has scheduled a trial for Jan. 3.

Mr. Walsh is a learned and experienced attorney who knows very well that he cannot ask a court to prevent publication of this book. So perhaps his real objective is simply to delay publication until all his prosecutions and appeals have been concluded and he has had an opportunity to place his own version of events on the record in the form of a final report to the court that appointed him. But Judge Keenan has placed the dispute on a fast track, which makes sense. The prosecutor must produce a detailed list of his objections to the manuscript this week, which will clarify the issues and provide guidance and reassurance to the author.

It is probably galling to a lawyer of Mr. Walsh's stature that his youngest associate has been so quick to compile and make public details about the decision-making, personalities and legal strategy of the case. But that's no reason to impede publication. The final decision remains with the writer who may very well elect to proceed notwithstanding the possible consequences.