Since February 2003, Iranian physicist Shahram Rahatlou has been barred from entering the government lab where he worked. The security officials who came to his door never told him what he had done wrong. They said there would be no appeal.

The lab is not in Iran, but at the Stanford Linear Accelerator Center (SLAC) in California. Rahatlou had been working there for nearly five years when officers from the US Department of Energy (DOE) visited him. He had, by all accounts, been an exceptional physicist. SLAC is a purely academic laboratory, which houses no classified research, and the experiment on which he was working makes all its findings publicly available. Even the lab's scientific leaders don't know why Rahatlou was barred from the premises (see page 229).

The DOE, which manages nuclear weapons facilities in addition to running civilian laboratories such as SLAC, has a duty to protect national security. Since the attacks of 11 September 2001, it has subjected many foreign researchers to background checks. But in a democracy, those who come under suspicion should have the right to know the accusations that they face, and have the right to appeal.

Rahatlou may come from a state designated as a “sponsor of terror”, but he is also one of the most hard-working physicists in a collaboration of more than 600 researchers from 10 countries. It is time for the US government to take a second look at his case. The DOE says the matter cannot be discussed further because it is classified, but many scientific officials — including John Marburger, the president's science adviser — have high-level security clearance. It is up to them to find a way to give Rahatlou his day in court.

The shocking pictures that have emerged from the Abu Ghraib jail in Iraq have sullied the United States' reputation across the Islamic world. Rahatlou's case is not in the same league of infamy. But it adds to a damaging impression that US officials are prepared to ride roughshod over those they see as potential enemies in the ‘war on terror’. If US labs are to continue to attract the world's best scientific talent, visitors need to know that they will be treated with respect and dignity under the law.