Louis B. Schwartz, an influential legal scholar whose work helped bring about significant changes in the penal codes of many states, died on Jan. 23 in San Francisco. He was 89.

In 1962, the American Law Institute, an association of judges, law professors and practicing lawyers, endorsed a model penal code drawn up by Professor Schwartz of the University of Pennsylvania Law School and Professor Herbert Wechsler of Columbia University.

At the time it was regarded as one of the most important recent works of legal scholarship.

Professors Schwartz and Wechsler tried to take a fresh look at state criminal law, which over time had tended to become jumbled, confused and full of contradictions, and set out a clear and consistent framework to which all laws should conform.

This model penal code proved influential, and resulted in about 35 states' amending or codifying their laws to bring them closer in line with its provisions.

Courts also interpreted the law differently in the wake of the model code, legal scholars say.

The code addressed general questions such as when a former conviction should bar a new prosecution for the same offense, when it is permissible to use force in defense of person or property and how to set standards for determining legal insanity.

It also posited that criminal law should not punish any kind of sexual relations between consenting adults in private, and it sought to harmonize the sentences imposed for felonies.

Mr. Schwartz later was director of the National Commission on the Reform of Federal Criminal Law, which drew up similar proposals. But Congress never agreed on any substantial changes.

In the mid-1950's Professor Schwartz served on a panel that recommended repealing "fair trade" laws directed against cut-rate retail sales to the public. While he opposed such retail price regulations, he disagreed with some of the panel's findings, arguing that they would weaken antitrust law in general.

Louis Brown Schwartz was born on Feb. 24, 1913, in Philadelphia and graduated from the Wharton School in 1932 and the University of Pennsylvania Law School in 1935.

After serving with the Federal Securities and Exchange Commission and the Justice Department in Washington and two years as an officer in the Navy, he joined the University of Pennsylvania Law Faculty in 1946.

He was a visiting professor at Harvard, Columbia and Cambridge, and the Institute for Advanced Legal Studies at London University.

Professor Schwartz is survived by his wife, Mimi, and his daughters, Johanna and Victoria Schwartz of Philadelphia.