The nation's toughest state narcotics law - adopted at a cost of $76 million four years ago in the wake of the Nixon administration's law-and-order campaign - has failed dismally in reducing drug trafficking and related crime, according to an exhaustive study by the New York City Bar Association.

Illegal drug use was not contained any better in New York State than in states without such a law, and crime associated with heroin users actually increased sharply during the first three years the law was in effect, the lawyer's study found.

Moreover, the bar association said that certain types of narcotics use have increased, and that criminal court systems have become hopelessly clogged with prolonged trials that might have been avoided without the drug law.

The important lesson from the New York experience, according to the study, is that passing tough new anti-crime laws without entirely overhauling the criminal justice system is a futile venture.

The half-dozen states now considering adopting such laws - including Massachusetts, Pennsylvania and Michigan - would do well to consider what happened to New York, the bar association panel concluded.

With considerable fanfare and national attention, then-Gov. Nelson A. Rockefeller signed the law in September, 1973, calling it a milestone in the nation's war against crime.

Intended principally to frighten drug users out of their habit and push drug dealers out of their trade, it provided 25-year-to-life sentences for high-level traffickers and indeterminate prison terms of eight years to life for street pushers caught with one-eighth of an ounce or more of narcotics.

Mandatory prison terms for second offenders were ordered, and anybody convicted of drug law violations was automatically subject to lifetime parole supervision. Relatively minor drug violations that had been misdemeanors were elevated to felony status, and offenders were no longer allowed to bargain felong charges down to misdemeanors.

Just a week after the law went into effect, Rockefeller claimed that heroin "seems to be drying up in the city," and he hailed the hard-line program as a step toward restoring civil order in New York State. At the same time, civil libertarians condemned it as a repressive "police state" measure, and predicted it would fail.

By the middle of last year, the state had spent $76 million administering the law, the bulk of it to add 49 judges to the bench along with new prosecutors and support personnel. Most of the judges were assigned to New York City, where the narcotics problem is most severe.

The bar association, with nearly $1 million in grants from the Justice Department's Law Enforcement Assistance Administration and the Drug Abuse Council, assembled a team of lawyers, police officials, judges, prosecutors, doctors, prison administrators and statisticians to anlyze the impact of the new law.

They concluded that, "Despite expenditure of substantial resources, neither of the objectives of the 1973 drug law was achieved. Neither heroin use nor drug-related crime declined in New York State."

Among the major findings:

Heroin use remains at least as widespread now, and this pattern is not appreciably different from other East Coast cities, thereby diminishing the possible argument that drug use would have grown worse without the law. This conclusion is based on narcotics deaths and instances of serum hepatitis, a disease normally associated with heroin use.

Serious property crime of the kind normally associated with heroin users increased sharply from 1973 to 1976 in a pattern similar to nearby states. Felonious property crimes rose 15 per cent, compared to an average rise of 14 per cent in Pennsylvania, Maryland and New Jersey.

Mandatory prison terms for second offenders did not deter drug offenses, and the risk that anybody arrested on narcotics charges would be sent to prison did not increase statistically during the last four years.

The time required to dispose of drug cases in city courts nearly doubled, because the ban on plea bargaining and the tough sentences discouraged guilty pleas. As a result, the backlog of narcotics cases awaiting jury trial has risen to 2,600 - nearly a year's workload.

"The depressing conclusion of all this is that even though many new judges were added at great cost, the aggregate rate of disposition of cases remained exactly the same," Bayless A. Manning, vice chairman of the drug law evaluation project, said at a news conference today.

The logjam of cases had a ripple effect, he said, that resulted in a smaller percentage of persons arrested being indicted, and a smaller percentage of persons indicted being convicted.

"A camel I can carry just so much on its back. If you put more of a load on it, it cannot carry it," Manning said.