This month Mahmoud Khalil, a recent Columbia University graduate who had worked with human rights groups and even the UK government, was detained in New York. His wife, who is eight months pregnant, said her husband was not told why he was being detained and that officers assumed he was on a visa – but actually he has a green card, allowing him to stay in the US and protecting his constitutional rights.

Khalil says his detention is part of a crackdown on dissent – and to deter others from protesting. During pro-Palestine protests on the Columbia campus last year he acted as a mediator between the university and the demonstrators, and, unlike many students, left his face uncovered. Then Donald Trump was elected US president and promised to clamp down on student protests.

Prof Joseph Howley, who knows Khalil, says he is “conspicuously committed to non-violent resolution of conflict, conspicuously committed to an inclusive vision of liberation and peace”. He tells Michael Safi why the implications of the government’s efforts to detain and deport Khalil are “incredibly chilling”.

Chris McGreal, who writes for Guardian US, explains the background to the case and whether free speech and the right to protest are safe in Trump’s America.