SAN DIEGO >> California’s governor has signed a bill that will give the terminally ill in the nation’s most populous state the right to end their lives with drugs prescribed by a doctor.

Right-to-die advocates have been pushing for decades to get such legislation passed in the state and say Monday’s signing is a major victory that could spur other states to follow suit.

Opponents disagree and are launching a drive for a referendum to overturn the law. They say similar bills in numerous states have stalled. The Catholic Church and advocates for people with disabilities say it legalizes premature suicide and puts terminally ill patients at risk for coerced death.

California is the fifth state to allow doctors to assist such deaths.

Here is a look at the states where the practice is legal.

WHICH STATE HAS THE LONGEST HISTORY WITH SUCH A LAW?

After a ballot initiative went into effect in 1998, Oregon became the first state to make it legal for a doctor to prescribe a life-ending drug to a terminally ill patient of sound mind who makes the request. Another ballot initiative in neighboring Washington made it legal in that state in 2008. In Montana, a 2009 state Supreme Court ruling found that nothing in state law expressly prohibits physician-assisted suicide, and that doctors could use a patient’s request for life-ending medication as a defense against criminal charges. Since then, the state Legislature has rejected bills each session that would either prohibit physician-assisted suicide or explicitly legitimize it in state law.

In 2013, Vermont’s legislature became the first in the nation to adopt it through legislation and not voter referendum.

HOW MANY PEOPLE HAVE OPTED FOR PHYSICIAN-ASSISTED DEATHS?

Since it was enacted, more than 850 people in Oregon have used the law to die as of Dec. 31, 2014. In Vermont, six people had requested life-ending drugs and lawmakers said they had not detected any abuse of the law. In Montana, no state agencies track how often it happens since it falls into a legal gray area. In Washington, 656 people have died after receiving a prescription for the drugs since 2009. Of those, Washington officials have verified 485 of them took the drugs, another 59 cases have not been confirmed and the rest died from health problems before taking their prescription.

WHAT DO WE KNOW ABOUT OREGON RESIDENTS WHO HAVE CHOSEN THIS OPTION?

Of the 155 patients for whom prescriptions were written last year, 94 ingested the medication and died and 37 died from their health problems before taking the drug. The median age of the deceased is 71. About 90 percent of those patients died at home and all had some form of health care insurance, although the number of patients who had only Medicare or Medicaid was higher than in previous years. Three of the patients who died during 2014 were referred for formal psychiatric or psychological evaluation. Prescribing physicians were present at the time of death for 14 of the 105 patients.

The median age of the deceased is 71. The patient must swallow the drug without help; it is illegal for a doctor to administer it.

HOW DOES CALIFORNIA’S LAW DIFFER FROM OREGON’S?

California modeled its bill after Oregon’s law but added more safeguards. The California measure applies only to mentally sound people and not those who are depressed or impaired. The bill includes requirements that patients be physically capable of taking the medication themselves, that two doctors approve it, that the patients submit several written requests and that there be two witnesses, one of whom is not a family member.

WHAT OTHER STATES ARE DEBATING THE ISSUE?

Bills introduced this year in at least two dozen states have stalled but right-to-die advocates emboldened by California’s actions are turning to New Jersey, where the state senate is slated to debate a bill this fall, and Massachusetts, where a legislative hearing on the issue is scheduled for later this month.

WHAT DO OPPONENTS SAY:

The Catholic Church and advocates for people with disabilities say measures like California’s legalize premature suicide and put terminally ill patients at risk for coerced death. Opponents in California filed paperwork with the state Tuesday to start their drive to collect signatures for a 2016 referendum to overturn the law.