When US district court judge Royce Lamberth last week threw out a 2009 lawsuit against federally funded research on human embryonic stem cells, he concluded that Congress has acted reasonably in supporting the work. It matters little that Lamberth made clear he was only grudgingly falling into line with a higher court's decision in April — he was right.

This reading of the law does not, and will never, satisfy those who see the work as unethical. But six successive, elected Congresses have seen fit to fund the research, and what began as a US$10-million investment by the National Institutes of Health (NIH) in 2002 has grown to an estimated $125 million this year.

Lamberth's judgment (see page 14) significantly diminished the chances of his decision being reversed on appeal by higher courts. Scientists who take NIH funds for this research can breathe a large, if not total, sigh of relief when it comes to legal challenges.

Still, it must be acknowledged that the lawsuit — and the decade of politics around stem cells that preceded it — has inflicted serious damage on the field. From one year to the next, and sometimes one month or day to the next, stem-cell researchers have not been able to count on reasonable and steady government funding. Stem-cell scientists interviewed last week were notably cool on the new ruling. For many, it is irrelevant, because they have moved to politically safe and scientifically exciting work with induced pluripotent stem cells. Others have retreated to using adult stem cells.

It is unknown how many young people have shunned careers in the field because of the uncertainty, but is likely to be a considerable number. Those established embryonic stem-cell scientists who have funding from private or state grants continue with the work, but even now many of them consider NIH funding to be unreliable given its volatile political profile. The law has got this one right, but being right is rarely enough.