The day after US President Donald Trump signed his now notorious Muslim ban, he spoke with Germany's Chancellor Angela Merkel. Over the phone, she reportedly "explained" to Trump the United States' obligations under international refugee law, which requires the international community to take in war refugees on humanitarian grounds.

It's hardly surprising that President Trump had to learn about the United States' responsibilities towards refugees from a foreign head of state. But it's clear that after only a week in office his administration's lack of familiarity with and respect for refugee and human rights law is already charting a dangerous course for the country and the world.

While the exact scope and meaning of the executive order continues to be deciphered, on its face and as applied to date, Trump's order appears to violate several international treaties ratified by the US, some provisions of which have been incorporated into US law and cited as binding by the US Supreme Court.

In particular, the order seems to fly in the face of the 1967 Protocol Relating to the Status of Refugees which updated the post-World War II Refugee Convention of 1951, and other international human rights law that prohibits discrimination on the basis of race, religion, or national origin.

Obligation to protect refugees

One of the reasons international law is so valuable is because the international community of nations has developed it as protection against such abuses, both in our country and around the world, often in the name of national security.

International law has learned from the past and made explicit that none of these violations can be excused by an appeal to national security, nor should they be permitted by an appeal to xenophobia.

The United Nations Refugee Convention requires that the US provide protection and safe haven to those facing persecution. By shutting the door to refugee admissions, whether temporarily or indefinitely, Trump's order flagrantly violates that core obligation. This order also breaks with the long US tradition and history (with some abhorrent exceptions that should never be repeated) of opening its doors to refugees.

The UN High Commissioner for Refugees and International Migration Organization noted this proud tradition in a joint statement in reaction to the executive order. "The long-standing US policy of welcoming refugees has created a win-win situation: it has saved the lives of some of the most vulnerable people in the world who have in turn enriched and strengthened their new societies," the statement read. "The contribution of refugees and migrants to their new homes worldwide has been overwhelmingly positive."

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Article 3 of the Refugee Convention makes clear that all signatory states "apply the provisions … to refugees without discrimination as to race, religion or country of origin". In 1980, Congress enacted the Refugee Act to bring the US into conformity with these obligations after ratifying the 1967 Protocol Relating to the Status of Refugees.

The legislative and negotiating histories of the Refugee Convention further make clear that discrimination by contracting states against different groups of refugees is a direct violation of the treaty.

While governments are responsible for designing their own refugee resettlement programmes, these programmes must conform to international obligations. They must select refugees for resettlement only on the basis of their needs, regardless of nationality, ethnicity, religion, or other related characteristics.

While the Convention allows exclusion of certain persons from refugee protection - for example, if they committed war crimes - this exclusion is determined on a case-by-case basis and certainly does not allow any sort of blanket ban against a group of people or nationality.

By halting admission of refugees from Syria, Trump has carved out an impermissible exception to a key US treaty obligation for a vulnerable community, one based solely on that community's country of origin. This is a clear violation of the Refugee Convention.

The national security argument

President Trump has further publicly and falsely stated that his order will protect our national security. But the UN High Commissioner for Refugees, acknowledging states' legitimate interests in maintaining public security and combating terrorism, has warned against the effects of making exceptions, or, in his words, "the erosion of long-standing refugee protection principles".

The most fundamental refugee legal principle incorporated into the Refugee Convention and obligatory even outside Convention ratification, is that of non-refoulement or not returning someone to a place where they are likely to be subjected to persecution.

This principle is widely understood to be an "essential … component of international refugee protection" and is echoed in another core human rights treaty to which the US is a state party, the Convention Against Torture (PDF).

While the order doesn't bar all Muslims from entering the US, barring immigration entry from seven majority-Muslim countries, especially when paired with his national security team's record of Islamophobia, leaves no doubt that Muslims are the target of this order.

Our core obligations under international law cannot be disposed of in times of real or, in this case, perceived political or national security crises.

To the contrary, it is in times of alarm, when governments are tempted to bow to their fears, that sticking to our core obligations and maintaining strong American leadership on the international stage is most important.

While Trump's order places a moratorium on refugee admissions and an indefinite halt on resettling refugees from Syria, the order leaves an exception for "religious minorities".

And while the order's language is neutral, the president stated in a recent interview with the Christian Broadcasting Company that he wants to provide priority to Christian refugees.

While the order doesn't bar all Muslims from entering the US, barring immigration entry from seven majority-Muslim countries, especially when paired with his national security team's record of Islamophobia, leaves no doubt that Muslims are the target of this order.

Racial profiling

But President Trump's un-American and unconstitutional action doesn't just violate the Refugee Convention - it flies in the face of other sources of international law that bind us.

The International Convention on the Elimination of All Forms of Racial Discrimination, or ICERD, to which the US is bound, requires states parties to "guarantee the right of everyone, without distinction as to race, colour, or national or ethnic origin, to equality before the law."

US violations of this treaty precede the Trump administration, and have already been so flagrant and obvious that nearly identical concerns were addressed by the ICERD's committee after 9/11.

The Committee expressed concern at the US government's discriminatory anti-terrorism measures and remarked that "measures taken in the fight against terrorism must not discriminate, in purpose or effect, on the grounds of race, colour, descent, or national or ethnic origin."

In 2008, the Committee specifically addressed the US government's racial profiling of Arabs, Muslims, and South Asians after the 9/11 attacks and the development of the National Security Entry-Exit Registration System for nationals of 25 countries, all located in the Middle East, South Asia or North Africa.

It observed that "measures taken in the fight against terrorism must not discriminate, in purpose or effect, on the grounds of race, colour, descent, or national or ethnic origin."

Aside from the institutionalised discrimination of Trump's Muslim ban, there is growing concern that it could be applied by border officials to sanction discriminatory questioning, profiling, and treatment of Muslim, South Asian, and Arab citizens and non-citizens at airports and elsewhere.

Discrimination of the vulnerable

The executive order also contravenes the International Covenant on Civil and Political Rights (ICCPR), another treaty to which the US is a state party.

Article 26 of the ICCPR requires equal treatment before the law of all persons, without discrimination on any ground, including race, religion, or national or social origin.

Article 4 of the ICCPR notes that even in a "time of public emergency which threatens the life of the nation", states cannot take any action to stray from their obligations that involve discrimination "solely on the ground of race, colour, sex, language, religion or social origin".

Trump's executive order further violates the ICCPR's prohibition against discrimination and equal protection before the law. The order is clearly discriminatory, requiring separate and unfair treatment of entire groups of people based on their national origin, Muslims in particular.

The Trump executive order not only denies individuals an opportunity for individualised review, but it has also resulted in the detention, denial of counsel, and removal of individuals with prior authorisation to enter the US.

Under human rights law, people are guaranteed an opportunity to adequately defend against deportation, especially under the ICCPR and Convention Against Torture.

The UN's Human Rights Committee, charged with monitoring compliance with the ICCPR, has already concluded that "xenophobia against non-nationals, particularly migrants, refugees, and asylum seekers, constitutes one of the main sources of contemporary racism and that human rights violations against members of such groups occur widely in the context of discriminatory, xenophobic and racist practices."

The international community has seen this before, and it has wisely created mechanisms to stop history from repeating itself.

The highest UN refugee officials have issued statements in recent years, anticipating and proscribing actions such as Trump's. After 9/11, the UN High Commissioner for Refugees stressed that "[a]ny discussion on security safeguards should start from the assumption that refugees are themselves escaping persecution and violence, including terrorist acts, and are not the perpetrators of such acts."

More recently, in response to the 2015 terrorist attacks in Paris, the High Commissioner expressed concern about states ending refugee resettlement programs or making refugee resettlement harder. "We are deeply disturbed by language that demonises refugees as a group," the High Commissioner's spokeswoman said. "This is dangerous as it will contribute to xenophobia and fear."

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Just this week, the UN High Commissioner for Refugees Filippo Grandi expressed deep concern about the "uncertainty facing thousands of refugees around the world who are in the process of being resettled to the United States."

He estimated that 20,000 refugees in precarious circumstances might have been resettled to the US during the 120 days covered by the suspension.

He noted that the people his agency refers to governments for resettlement are the "most vulnerable - such as people needing urgent medical assistance, survivors of torture, and women and girls at risk" and that "new homes provided by resettlement countries are life-saving for people who have no other options".

Reciprocal measures

Meanwhile, in mere days since the order was signed, many countries are considering taking reciprocal measures against US citizens. Trump's measure may likely further endanger the religious minorities he purports to defend.

International companies, academic institutions, and even the international air transport association have raised serious concerns regarding the detrimental impact of the order on their staff and ability to conduct business. Even Trump's own employees took a bold and public stance against the ban.

Trump's Muslim ban has enraged world leaders and was condemned by UN officials. The new secretary general of the UN, Antonio Guterres, said that Trump's executive actions "violate our basic principles … [and] are not effective if the objective is to indeed avoid terrorists to enter the United States."

And on Wednesday, several UN human rights experts issued a joint statement blasting Trump's immigration ban as discriminatory and in violation of US human rights obligations.

It shouldn't take the chancellor of another country or the top refugee and human rights officials in the world to tell President Trump that fear and xenophobia are no excuse for discrimination.

But if he won't listen to the UN or Chancellor Merkel or concerned companies, academic institutions, transport associations, human rights organisations, and over 100 diplomats, maybe he should listen to former US President Ronald Reagan, supposedly a hero of his. In 1980, a year after the Refugee Act was signed into law, the new president, just a few months into his presidency, re-affirmed the US' commitment to welcome the exiled.

"We shall continue America's tradition as a land that welcomes peoples from other countries," he said. "We shall also, with other countries, continue to share in the responsibility of welcoming and resettling those who flee oppression."

For once, Trump should listen, and heed the Gipper's words.

Jamil Dakwar is the director of the American Civil Liberties Union's Human Rights Program and adjunct lecturer at John Jay College at the City University of New York.

The views expressed in this article are the author's own and do not necessarily reflect Al Jazeera's editorial policy.