California became the first state in the nation to require either the chemical or surgical castration of repeat child molesters. By a 51 to 8 vote today, the state Assembly passed a bill already approved by the Senate that requires anyone convicted of two sexual assaults on minors to be injected with a drug that reduces sex drive, if they choose not to be surgically castrated at the government's expense.

Gov. Pete Wilson (R), who backed the measure as a step toward controlling what he called "deviant" behavior, has promised to sign the legislation.

Experts said that the new California law was the most severe measure in the nation aimed at child molesters. Similar legislation is being considered in Florida, Michigan, Massachusetts, Texas and Washington.

The law requires that anyone -- men and women -- convicted twice of sexually assaulting a child be injected during the week before parole with a drug containing female hormones that reduces sexual drive. They also have the option of surgical castration. Only a small percentage of repeat child molesters are women.

The drug most commonly employed, Depo-Provera, is used as a contraceptive in women. It has the effect of lowering testosterone levels in men, but can lower sexual desire in females as well when administered in large enough doses.

Depo-Provera would be injected weekly throughout the period of parole, which averages three years in California, because the drug's effects wear off over time. The use of drugs like Depo-Provera in several European countries has produced dramatic reductions in rates of recidivism, which has been estimated at 75 percent to nearly 100 percent, among child molesters.

Opponents of the new law expressed doubts about the effectiveness and legality of the new measure.

"What we are talking about is forcibly medicating people," said Katherine Sher, legislative advocate for the California Attorneys for Criminal Justice. "It goes to some fundamental constitutional rights."

Sher said that she expected the law to be quickly challenged as a violation of 8th Amendment guarantees against cruel and unusual punishment, as well as on a variety of constitutional privacy protections.

The American Civil Liberties Union and other groups also have opposed the measure on the ground that it constitutes a violation of procreative freedoms.

Fred Berlin, a physician and a professor of medicine at Johns Hopkins University in Baltimore, has used Depo-Provera effectively in treating people with sexual disorders. But he said the new law was too simplistic because the actions of many molesters are rooted in psychological disorders, not elevated levels of testosterone.

"There are certain kinds of criminal behavior that are related to mental disorders, but we treat them as simple criminals," Berlin said. "We treat tax evasion and pedophilia the same."