A U.S. district court judge has blocked federal funding for human embryonic stem cell research, overturning guidelines crafted by the Obama administration to fund such work.

The injunction will have a significant negative impact on the field, says Arnold Kriegstein, director of the Center of Regeneration Medicine and Stem Cell Research at the University of California, San Francisco.

Research using human embryonic stem cell lines created with private funding was made eligible for federal funding under new National Institutes of Health guidelines and an executive order from President Barack Obama in 2009. That order had reversed limits enacted by George W. Bush confining federal funding to projects using stem cell lines created before August 2001.

The new policy relieved researchers from having to silo federal and non-federal research into different operations, a burden that limited collaboration and necessitated the purchase of duplicative lab equipment.

The new ruling, published August 23 by U.S. District Court Judge Royce C. Lambert, determines that all human embryonic stem cell research is research in which a human embryo is destroyed and is thus prohibited by the Dickey-Wicker Amendment, a 1995 law that prohibited using federal funds to create human embryos for research purposes or for research in which human embryos are destroyed, discarded, or knowingly subjected to risk of injury or death greater than that allowed for research on fetuses in utero.

"The language of the statute reflects the unambiguous intent of Congress to enact a broad prohibition of funding research in which a human embryo is destroyed," says Lambert in his ruling on the case.

In assessing a balance of hardships en route to issuing the temporary injunction, Lambert wrote that “the harm to individuals who suffer from diseases that one day may be treatable as a result of human embryonic stem cells research is speculative” and that it remain uncertain whether such research would result in “new and successful treatments for diseases such as Alzheimer’s and Parkinson’s disease.”

The Justice Department is reviewing the decision.