Harvard sued and asked for a restraining order less than 24 hours after the Trump administration had said it would block current and future international students from attending the university.

Harvard University is challenging the Trump administration's decision to bar the Ivy League school from enrolling foreign students, calling it unconstitutional retaliation for defying the White House's political demands. It is the school's second suit against the Trump administration.

A federal judge blocked President Trump's order banning international students at Harvard, but the effort has prompted concern at campuses nationwide among students and university leaders.