President Trump’s counterterrorism executive order keeping out many refugees, immigrants, visitors, and even residents demonstrated how shoddy policymaking can have grave political, moral, and security consequences.

Acting on Trump’s new executive order, border officials on Saturday detained people at airports who had already been granted entry visas. They also detained some lawful permanent residents who unluckily booked their flights back home to the U.S. for the day after Trump’s hasty rule.