Harvard University is challenging President Donald Trump’s move to block foreign students from coming to the United States to attend the Ivy League school, calling it illegal retaliation for Harvard’s rejection of White House demands.

Trump cited national security concerns as justification for barring international students from entering the U.S. to pursue studies at Harvard.

The Trump administration has tried repeatedly to restrict Harvard's ability to enroll international students — a serious threat for a school where more than one in four students hail from foreign countries .