IT HAS BEEN more than four years since the Justice Department began investigating allegations that presidential adviser Hamilton Jordan used cocaine. Mr. Jordan was, ultimately, completely exonerated. But this did not happen until after a special prosecutor had been appointed under the Ethics in Government Act and after Mr. Jordan had incurred sizable debts to the attorneys he engaged, at his own expense, to make his defense.

There was a lot that was disturbing about that whole proceeding. The allegations were made during plea-bargaining discussions by two big-time tax evaders--scarcely the most credible of witnesses. Attorney General Benjamin Civiletti and the judges who appointed the prosecutor said they had no choice because of the wording of the law, even though the alleged misconduct was not the kind Congress had in mind in passing the legislation. Mr. Civiletti also said he could not dismiss the allegations as without basis because several witnesses refused to talk to him without immunity--something the attorney general had no authority to extend. Mr. Jordan's decision to stay in office and fight was reassuring: officials shouldn't allow themselves to be driven from office by unsubstantiated allegations. But the price he had to pay, in terms of finances and personal discomfort, was high.

This episode persuaded just about everyone that the law needed changing, and last year Congress changed it. Now the attorney general, in investigating charges made against a public official, is required to consider the specificity of the charges and the credibility of the source of information--two factors that might have persuaded Mr. Civiletti that there were legal grounds not to appoint a special prosecutor in the Jordan case. The law also provides that subjects of these investigations can be reimbursed by the court for attorney's fees when no indictment is brought and if the fees would not have been incurred except for the investigation. So future public officials are not likely to incur sizable debts to defend themselves against baseless allegations, as Mr. Jordan did.

In the meantime, Mr. Jordan still has debts greater than his annual salary as a presidential aide. He has declined offers of private contributions to pay them and has not in any way sought to get reimbursement from the government. Simple justice requires that the government reimburse him for his legal expenses. If the revised law does not authorize that, a special law can and should be passed.