The US Food and Drug Administration (FDA) can block US clinics that offer cultured cell products, according to a ruling of a US district court this week.

Although championed by politicians such as Texas governor Rick Perry, clinics marketing stem-cell procedures worry many health-care advocates, because these procedures are often not thoroughly tested in clinical trials (see Nature‘s ‘Stem-cell therapy takes off in Texas’ and warnings compiled by the International Society for Stem Cell Research).

If cells are harvested and returned to a patient with ‘minimal manipulation’, the procedures are not regulated, but further processing classifies cell treatments as a drug, which requires FDA approval.

Legal action in the recent court decision began in 2008, when the FDA moved against Regenerative Sciences, based in Broomfield, Colorado, which offered to treat joint and other problems by collecting patients’ stem cells, then sorting, culturing and re-injecting them.

The medical director of Regenerative Sciences challenged the FDA, maintaining that the treatment is not subject to FDA regulation because it uses a patient’s own cells.

However, a court ruled on Monday that the clinic’s product was a drug and granted the FDA’s request for a permanent injunction against the company. Presumably, the ruling paves the way for further crack-downs. Alternately, it may cause more stem-cell tourism, in which desperate US patients seek treatment abroad, in clinics with even less regulation.