Harvard University is calling President Donald Trump’s proclamation to block foreign students from attending the university another “illegal retaliatory step.”

“This is yet another illegal retaliatory step taken by the administration in violation of Harvard’s First Amendment rights,” Harvard said in a statement. “Harvard will continue to protect its international students.”

Trump signed the proclamation on Wednesday afternoon, invoking the Immigration and Nationality Act to prohibit the entry of noncitizens from entering the U.S. to study at Harvard for at least six months. Trump argued the institution is “no longer a trustworthy steward” of international students.

The proclamation also directed the secretary of state to consider revoking the visas of foreign students already in the U.S. to study at Harvard.

“I have determined that the entry of the class of foreign nationals described above is detrimental to the interests of the United States because, in my judgment, Harvard’s conduct has rendered it an unsuitable destination for foreign students and researchers,” the proclamation said.

Last month, the Department of Homeland Security tried to revoke Harvard’s Student and Exchange Visitor Program — which allows the school to sponsor foreign students – but a federal judge issued a temporary order blocking the move.

Trump justified the sudden move Wednesday by claiming Harvard has refused to provide information about international students, has “extensive entanglements with foreign countries,” and has discriminated in their admissions practices. The proclamation also claimed crime rates have “drastically risen” at the school and requires the government to probe the potential misconduct of foreign students.

“These concerns have compelled the Federal Government to conclude that Harvard University is no longer a trustworthy steward of international student and exchange visitor programs,” the proclamation said.