There are good reasons why scientific misconduct tends not to be punishable in law. The distinctions between bad science, sloppiness, data manipulation and purposeful fraud are subtle and often difficult to establish. Fabricated results tend to be discovered, thanks to the self-regulating mechanism of research replication. Scientists will find their own means of punishment.

The case of Jan Hendrik Schön shows how effective this mechanism can be. The rise of the young German physicist at Bell Laboratories in New Jersey ended abruptly two years ago when the inability of competing groups to reproduce his results led to him being found to have fabricated data in at least 16 high-profile publications. Almost overnight, the former wunderkind became a persona non grata.

The University of Konstanz has now decided that this is not the end of the story. In a bid to repair the damage done to the reputation of science, it has withdrawn Schön's PhD, which he obtained there in 1997 (see Nature 429, 692; 2004). An internal investigation last year concluded that his thesis was free of false data. But the university says that Schön has abused his entrance ticket to the academic world in such a malicious and irresponsible way that he forfeited his academic consecration. The “dignity” of the doctorate is at stake, it says.

Some will applaud this move. It is a clear warning to all scientists that honesty and good practice are life-long duties. The University of Konstanz, after all, has a right to dissociate itself from fraudsters taking advantage of its name. And when it comes to scientific misconduct, surely we need a policy of zero tolerance.

Well, yes, up to a point. But there is a sense that scientists are taking revenge for a particularly high-profile piece of misconduct that cast a wide shadow. Is Schön being made a scapegoat for the community's broader imperfections? And is it more reprehensible to cheat in physics than in biomedicine? After all, no one ever questioned the PhDs of Germany's most notorious science fraudsters, cancer researchers Friedhelm Hermann and Marion Brach, who fabricated data in about 100 papers.

At the heart of the issue is a question about the status of a PhD. The dignity of the degree is more threatened by the tens of thousands of fake PhDs available for sale than by one researcher going astray. No one doubts that Schön obtained his doctorate for a scientific achievement. The decision to revoke it implies that the PhD is a club membership that can be withdrawn. Nature, on the other hand, sees the PhD as a piece of history that cannot, and should not, be rewritten.