Iranian physicians in North America faced an unsettling constraint this month. Between 29 May and 5 June, the US Educational Commission for Foreign Medical Graduates (ECFMG) stopped processing requests to verify credentials issued by Iranian institutions, pending clarification of restrictions on interactions between US and Iranian medical and educational organizations (see go.nature.com/jrcxzz). The Medical Council of Canada, which also uses the ECFMG, made a similar announcement.

Iranian citizens are among the top ten groups of international physicians who acquired US certification in 2009 (see go.nature.com/ecmnkb) and were the largest group among immigrants entering post-medical training in Canada in the same year (see go.nature.com/95ayyf).

As Richard Nephew — a former senior US official and leading sanctions architect — has warned, there is a risk that the US foreign-policy tool of using sanctions to isolate Iran could backfire (see go.nature.com/ocrini).