Challenging a resistant Bush administration and Congress, California on Sunday became the only state in the nation to adopt its own law funding and expanding embryonic stem cell research.

Still in early stages at universities and biotechnology firms -- many of them in California -- such research holds the hope of treating ailments from Parkinson's to cancer to diabetes to spinal cord injuries. But its sci-fi nature and proximity to issues such as abortion and cloning have prompted calls in several states and at the federal level to ban the research.

Last year, Bush restricted federal funding for human embryonic stem cell research to a select number of existing cell lines. Critics say many of those stem cells are in poor condition and are useless for research.

There was no comment Sunday afternoon from Bush.

Significant opposition remains in California. The California ProLife Council, the Committee on Moral Concerns, and the Christian Coalition of California opposed the bill.

"I hope this is immediately challenged in court," said Michael Mears, executive director of the Sacramento-based Capitol Resource Institute. The group supports research on adult stem cells but opposes embryonic research, which involves destroying the embryo to use the cells.

"We're talking about human life here," Mears said.

Congress is deadlocked over how to proceed on several levels, and federal funding is limited to narrow research parameters.

In signing the legislation Sunday, Gov. Gray Davis said he hopes to turn the national tide.

"Stem cell research is responsible research with the potential to save millions of lives," the governor said. "Debate will range back and forth in this country. As the country ages, however, I believe more and more Americans will see the value stem cell research has in enhancing the quality of life for the people they love."

The bill was one of hundreds Davis is evaluating before a Sept. 30 deadline. Today, Davis plans to sign SB 1661, which would make California the first state in the nation to grant workers paid family leave.

The measure would give millions of workers up to six weeks of annual family leave, during which they would earn partial pay from the state's disability insurance program. Employees could use their leave to care for newborns or recently adopted children, as well as for any relative or domestic partner suffering from a serious illness.

Businesses are opposed because they believe the loss of employees for weeks at a time would reduce productivity, particularly for smaller companies.

Researchers said the stem cell law gives them several assurances.

"You have the hope if you're a scientist working in this area that when you wake up tomorrow, it's not going to be illegal," said Larry Goldstein, a UC San Diego geneticist hoping to treat Lou Gehrig's disease through stem cell research.

Stem cells, particularly those extracted from embryos, are thought to be versatile enough to yield specialized cells that can repair specific parts of the body. Researchers hope to discover how to make insulin-producing cells for diabetics, brain cells for Parkinson's sufferers, cancer-killing and organ-rebuilding cells for cancer patients and nerve cells for people with spinal cord injuries. The legislation signed by the governor -- SB 253 by Sen. Deborah Ortiz, D-Sacramento -- covers research using stem cells from human embryos and from adults, as well as research to create personalized stem cell lines by infusing DNA from the person seeking treatment into an unfertilized egg. The law allows state money to be used even on stem cell lines that can't currently receive federal funding.

The law requires health care workers at in-vitro clinics to inform patients that they may donate unused embryos for stem cell research. Fetal tissue also may continue to be donated.

The law prohibits the sale of embryos or fetal tissue and establishes an institutional review board to oversee stem cell research policies and procedures. A separate measure also signed into law by the governor makes permanent a temporary ban on human reproductive cloning.

Actor Christopher Reeve, a spokesman for stem cell research after a 1995 accident crushed his spinal cord and paralyzed him, applauded the law.

"Since embryonic stem cells were first isolated in 1998, political debate has had a chilling effect on our scientists," said Reeve, who joined the governor and research advocates by telephone Sunday. "It's my hope that with the leadership in California, there will be a groundswell of support."

It's unclear how much state money the legislation will draw in the near future. The surplus of the late 1990s allowed California to set aside tens of millions of dollars for biomedical research. But California's recent economic troubles have left the state a budget deficit from which it could take years to emerge. Until then, researchers looking for new sources of money still will rely heavily on the federal government and private investors.