A few days before they were to submit a scientific paper together, an evolutionary biologist in Europe received an unexpected request from two co-authors in the United States.

After much thought, the co-authors said they preferred not to risk publishing at this time. One had just lost a job because of a canceled government grant; the other feared a similar fate if they went ahead with the paper. Although both were legally in the U.S., they worried they might lose their residency if their names appeared on a potentially controversial article.