The US Commerce Department called for public comments last March on a proposal to expand restrictions on the sharing of advanced research and technology with foreign nationals. The result was an outpouring of opposition, particularly from universities, which have already seen the enrolment of foreign students shrink because of new visa requirements adopted after September 11 2001.

“I sit writing this letter one block from the site of the first self-sustaining chain reaction, produced in the 1940s by Enrico Fermi and collaborators,” wrote Simon Swordy, a professor of physics, astronomy and astrophysics at the University of Chicago, in one of more than 300 comments on the proposal, running to more than 1,100 pages.