"THE TRUTH IS, we have a leniency problem," one New Yorker wrote in a recent letter to The New York Times. "Attacking the causes of crime will have no short-term effect. So, let's get tough." The sentiment is widespread and understandable. In our view, it is also shortsighted. Substandard social conditions and the failings of the criminals. Merely "getting tough" with criminals without regard for some of these related aspects of the crime problem is likely to be a futile exercise. In no area of law enforcement is this more apparent than in attempts to reduce illegal drug activity. And the classic example of the failure of a one-dimensional effort to deal with the drug problem is the New York State Drug of 1973.

Four years ago, then-Gov. Nelson Rockefeller, with considerable fanfare, supported and signed legislation that he said would substantially reduce illegal drug activity in the state. THe controversial measure almost completely eliminated judicial discretion from the sentencing process and established harsh, mandatory penalities - ranging from one year to life in prison - for those convicted of using drugs, selling drugs or committing a drug-related crime. The law raised from misdemeanor to felony status the sale and possession of several drugs, including some that are non-addictive. And it barred plea-bargaining for persons arrested for any but the least serious violations. Gov. Rockefeller brushed aside criticisms from judges, bar associations, police and civil libertarians that the law was draconian and/or unworkable.

Recently the Joint Committee on New York Drug Law Evaluation released its three-year study of the Rockefeller law's impact. The report's conclusion: Despite the $76 million spent to provide new judges, other court personnel and court facilities to handle the increased case load, the law did not reduce either illegal drug use or dur-related crime; illegal drug activity flourished in New York City and throughout the state at about the same levels as in nearby cities and states without such a law.

The report states that the existing congestion in the New York City courts and the increased time taken up by the trials of persons indicted under the 1973 law-worked to lessen its deterrent effect. Even in one upstate county where there was no court backlog, illegal drug activity during the three-year study period continued unchecked. This would seem to support the view that the legislation's basic flaw was that it dealt too narrowly with sentencing, while ignoring the necessity of addressing the entire criminal justice system.

The unwritten conclusion of this report is that the Rockefeller statue was a bad law - one drafted in anger and frustration and with a greater interest in gaining immediate political credit than in fashioning an effective battle plan in the war on drugs. The written conclusion, which makes good sense to us, is that illicit drug use "is deeply rooted in broader social maladies" and is "part of a wider complex of problems. . . . It is implausible that social problemas basic as these can be effectively solved [only] by the criminal law."