Europe's largest basic-research agency, the CNRS in France, is now vetting not only non-European Union (EU) researchers working on sensitive topics, but also all scientists from Iran regardless of what they work on. Researchers allege that the move exacerbates an already difficult situation in which visa applications are denied based on nationality.

A 12 November memo, relayed by the CNRS's security office from the state national security and industrial espionage services, requires that all projects with Iran go through formal security screening, to identify ones potentially meriting further scrutiny. It translates UN sanctions that call for member states not to provide Iran with technical assistance or training that might be used for the proliferation of weapons of mass destruction, says Joseph Illand, who heads the CNRS security office.

It's the first case Illand can recall of such an explicit country-specific instruction at the CNRS — although similar, if unwritten, restrictions have in practice long been in effect for Iran and other countries considered as security risks. Given the threat of proliferation, such extra scrutiny is normal, he says.

The rules expand on those introduced in January 2005, which require extra scrutiny for visits from non-EU scientists whose work relates to an undisclosed list of 'sensitive' laboratories or topics. In such cases, the heads of host laboratories must give details of proposed visits, and their opinion of the visitor, to security authorities. For less-sensitive laboratories, lab heads need only declare foreign visitors monthly, whereas no-risk labs must simply maintain an internal register that can be consulted by authorities if needed.

They need to stop looking at researchers' passports, and start looking at their work.

In recent years, Iranian researchers have struggled for academic equality and scientific access. In July, for instance, the Netherlands banned Iranians from accessing nuclear laboratories or courses, and the United States has subjected Iranian visa requests to lengthy interagency reviews in the wake of the terrorist attacks of 11 September 2001. Britain last year also introduced tough vetting of non-EU science students.

The fact that France is cracking down on Iranian researchers doesn't surprise Carthage Smith, deputy executive director for the International Council for Science in Paris, and a member of its human-rights committee. "There are legitimate concerns in the international community at present about the risk of technology transfer to Iran and other specific countries," he says. "We can't ignore that."

But he worries about how the rules might be implemented. "Any vetting must be separate from country lists, with each individual case being judged on its merits," he says. Otherwise, overzealous bureaucrats could turn country listings into effective blacklists. Formalizing extra vetting for Iranian researchers may have secondary effects, admits Illand, in that French hosts might show less interest in collaborating with Iranians to avoid administrative hassle, or government bureaucrats may be tempted to play safe and turn down visa applications. Many within the CNRS and the French administration, he says, support greater collaboration with Iran as a form of scientific diplomacy.

Overall statistics are not available, but Nature has gathered complaints from more than a dozen Iranian scientists who allege that French authorities recently either refused their requests for visas or simply never responded.

Take Ali Tahzibi, a mathematician and Iranian national at the Federal University of São Carlos in Brazil. In July he applied for a visa to work for a year, starting in October, with Christian Bonatti at the CNRS's Institute of Mathematics, part of the University of Bourgogne in Dijon. Tahzibi took a year's sabbatical, bought plane tickets for himself and his family, rented an apartment in Dijon, and arranged schooling for his son. The visa never materialized. "To wait up until just hours before your flight in the hope of getting a visa without obtaining any response was torture for a family with a little child," says Tahzibi.

Visa-seeking researchers share common stories of being passed back and forth within the French bureaucracy. "It's a typical administrative vicious circle," says Pierre Sens, a researcher at the Paris Industrial Physics and Chemistry Higher Educational Institution, who tried to intervene on behalf of a former postdoc and Iranian national. The office of Valérie Pécresse, the minister of research and higher education, declined to comment on the allegations or their impact on collaboration, instead referring Nature to the ministry of immigration.

The cases and the CNRS policy are "absolutely astonishing, if not scandalous on the part of a country such as France, which sees itself as the cradle of human rights", says Thierry Dauxois, a CNRS physicist at the Ecole Normale Supérieure in Lyon. "They need to stop looking at researchers' passports, and start looking at their work."