Immediately, there were numerous protests and legal challenges, with some calling it a "Muslim ban" because all of the affected countries had a Muslim majority. A nationwide temporary restraining order (TRO) was issued on 3 February 2017 in the case Washington v. Trump, which was upheld by the United States Court of Appeals for the Ninth Circuit on 9 February 2017. Consequently, the Department of Homeland Security (DHS) stopped enforcing portions of the order and the State Department re-validated visas that had been previously revoked. The order was criticized by members of Congress from both parties, universities, business leaders, Catholic bishops, top United Nations officials, a group of 40 Nobel laureates, Jewish organizations, 1,000 U.S. diplomats who signed a dissent cable, thousands of academics, and longstanding U.S. allies.
Key provisions of executive orders 13769 and 13780 cite to paragraph (f) of Title 8 of the United States Code § 1182, which discusses inadmissible aliens. Paragraph (f) states:
Whenever the President finds that the entry of any aliens or of any class of aliens into the United States would be detrimental to the interests of the United States, he may by proclamation, and for such period as he shall deem necessary, suspend the entry of all aliens or any class of aliens as immigrants or nonimmigrants, or impose on the entry of aliens any restrictions he may deem to be appropriate.
The act that underlies this, known as the Immigration and Nationality Act of 1952 (a.k.a. the McCarran–Walter Act), was amended by the Immigration and Nationality Act of 1965 (a.k.a. the Hart−Celler Act), which included a provision stating
No person shall receive any preference or priority or be discriminated against in the issuance of an immigrant visa because of the person's race, sex, nationality, place of birth, or place of residence. The language in the INA of 1965 is among the reasons District of Maryland Judge Chuang issued a temporary restraining order blocking Section 2(c) of Executive Order 13780.