California Gov. Jerry Brown. (Damian Dovarganes/Associated Press)

CALIFORNIA GOV. Jerry Brown (D) has signed a bill allowing doctors to prescribe lethal drugs to terminally ill patients who want to hasten their deaths. That makes California the fifth — and largest — state to permit medical aid in dying. It is a victory for the death-with-dignity movement that may inspire other states to follow. It is critical that the state implement the measure with the same care that characterized its deliberations.

The End of Life Option Act, modeled on a law implemented in Oregon in 1997, was signed by Mr. Brown on Monday. The measure will take effect next year. It permits physicians to provide lethal prescriptions to mentally competent adults who have a terminal illness and are expected to die within six months. Agreement from two physicians is required, and the medicine must be self-administered.

The bill passed California’s legislature Sept. 11 after prolonged, emotional debate, and Mr. Brown then struggled with whether to sign it . The governor is a former Jesuit seminary student and a cancer survivor, so the complex issues raised by the measure had personal resonance for him.

“The crux of the matter,” he wrote in a perfectly calibrated signing statement, “is whether the state of California should continue to make it a crime for a dying person to end his life.” He discussed the question with many people, including doctors, advocates for the disabled and religious leaders. In the end, he said he was left to reflect on what he would want “in the face of my own death”; while he doesn’t know what he would do, he wrote, it “would be a comfort” to be able to consider options.

Oregon’s experience supports that conclusion. Its law has been invoked sparingly, with 1,327 prescriptions written in the past 17 years; of that number, 468 patients opted not to use the medicine. Fears that the elderly might be coerced by greedy heirs or unscrupulous doctors have not materialized. But just as in Oregon, it will be important that California require strict compliance, with good data collection and vigilant oversight. California’s enactment of this law means that more than 1 in 10 Americans will have the option of aid-in-dying. How well California implements its law could help determine if residents of other states will be able to find similar comfort.