Within days of taking up his role as president of the United States, Donald Trump signed a series of executive orders. One such order suspended all refugees from entering the U.S. and banned travellers from seven predominantly Muslim countries. And it affected many foreign-born Americans, even those with visas and green cards. The ban drew immediate outrage and criticism both in America and around the world. But as the courts decided on the legality of the order, it was the constitution of the United States that was under challenge.