WASHINGTON President Donald Trump says that his executive order restricting immigration and travel from certain predominantly Muslim countries isnt a ban on Muslims coming to the U.S., but Trump himself has given reason to think otherwise.

To be clear, this is not a Muslim ban, as the media is falsely reporting, Trump said in a Sunday statement , as furor over the order prompted mass protests across the country.

This is not about religion this is about terror and keeping our country safe, the president continued. There are over 40 different countries worldwide that are majority Muslim that are not affected by this order.

During his presidential campaign Trump said he wanted a total and complete shutdown of Muslims entering the United States, a proposal that came to be known as a Muslim ban. The Trump campaign later said it wanted extreme vetting of anyone from certain countries seeking refugee status in the U.S.

Banning people based on their religion would be a clear violation of the First Amendment of the U.S. Constitution, which says the government shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof. In other words, the government cant make a policy targeting people based on their religion.

Even some Republicans think the order is constitutionally questionable. Sen. Lamar Alexander (R-Tenn.) said it hadnt been carefully written.

And while not explicitly a religious test, it comes close to one which is inconsistent with our American character, Alexander said.

Trumps order restricted entry into the U.S. for any non-American citizens originally from seven countries with predominantly Muslim populations: Iran, Iraq, Libya, Somalia, Sudan, Syria and Yemen. It also suspended all refugee resettlement for 120 days and barred Syrian refugees indefinitely. Federal judges have halted parts of the order and customs officials have enforced it different ways at different airports, causing chaos and confusion . For a period, the government was refusing entry even to legal permanent residents, before officials said they would be admitted on a case-by-case basis.

The American Civil Liberties Union and other groups that filed lawsuits over the order are not impressed by Trumps point that people traveling from many other Muslim countries are unaffected by the order.

We have no doubt that the motivation behind the executive order was discriminatory, ACLU director Anthony Romero said in a statement . This was a Muslim ban wrapped in a paper-thin national security rationale.

Despite his protestation to the contrary, Trump himself described the order as the ban on Monday in a Twitter message . He also said that he would prioritize resettlement of Christian refugees, and the order contains an exemption for religious minorities facing persecution.

Do you know if you were a Christian in Syria, it was impossible, at least very tough, to get into the United States? Trump said Saturday . If you were a Muslim, you could come in, but if you were a Christian, it was almost impossible.

Trump adviser Rudy Giuliani, the former mayor of New York City, said Saturday that the policy grew out of Trumps original proposal to shut down Muslim immigration. When he first announced it, he said Muslim ban, Giuliani said in a Fox News interview . He called me up and said, Put a commission together, show me the right way to do it legally.

While the order itself doesnt mention any religions by name, comments by Trump and others could affect how federal courts interpret the order. Abner Greene, a law professor at Fordham University, said that the Supreme Court has previously struck down ostensibly religion-neutral laws because of the broader context in which the laws were written.

Trumps comments are harmful to the administration on this issue, Greene said. Stuff he said in the campaign and since taking office would be fair game.

Elise Foley contributed reporting to this story.