“Citizenship, then and now, was the right to have rights — to freely participate in our political community. The Framers of the Fourteenth Amendment extended that promise to 'every free-born person in this land.' … We keep that promise today.” So concludes the decision of the Supreme Court in the landmark case Trump v. Barbara, affirming the constitutional right to birthright citizenship and rejecting President Trump’s attempt to end it. Trump’s executive order had aimed to prevent babies born to undocumented immigrants and temporary foreign residents from automatically becoming American citizens. We speak to Columbia University historian of immigration Mae Ngai about the case and the white nationalist logic behind Trump’s challenge.