Trump has said the travel ban is necessary to protect the United States from terrorism by Islamic militants. Sanders says if the ban were eliminated, "the United States may be forced to unsuspectingly allow unsafe criminals or terrorists into the country". They also argue that his policy amounts to the Muslim ban that he called for as a candidate, violating the Constitution's prohibition against religious bias.
The controversial ban restricts visitors from five Muslim countries, North Korea and Venezuela.
Just one week into his presidency on January 27, 2017, Trump followed through with a campaign promise and announced a 90-day ban on travelers from Iran, Iraq, Libya, Somalia, Sudan, Syria and Yemen.
Opponents, led at the high court by Hawaii, say Trump overstepped his authority and was motivated by anti-Muslim animus.
But Trump's lawyer, Solicitor General Noel Francisco, said any comments the president made on the stump should be entirely "out of bounds" in the Supreme Court. Demonstrators protesting the ban filled the area outside the building.
Following the Supreme Court's deliberation, we are hopeful that these bans, in all their forms, will be relegated to the footnotes of history.
The justices took turns questioning.
"This is an out-of-the-box kind of president in my hypothetical", responded Kagan, drawing laughter.
"We don't have those, Your Honor", Francisco replied.
Justice Stephen Breyer to Francisco: "It seems to me that there are probably a significant number of such people [eligible for case-by-case waivers of the travel ban]".
Rather, he said, it is about whether the president has the authority to modify laws that Congress already passed-specifically, lawmakers' decision not to discriminate on the basis of nationality.
Demonstrators that gathered outside of the courthouse Wednesday morning as rain fell held signs that read "No Muslim Ban".
"So you want the president to say, 'I'm convinced that in six months we're going to have a safe world?'" Kennedy asked.
Kennedy added: Do courts have the obligation to review whether there's a national emergency that justifies that presidential leeway?
Another of the Trump Administration's immigration policies is also under challenge.
Mr. Francisco urged the justices to ignore Mr. Trump's campaign statements.The oath of office transformed Mr. Trump, his lawyer said.
Kennedy pressed on that point.
Francisco replied that the justices would not necessarily be barred from considering the previous statements, but argued that if the president's hypothetical Cabinet had presented a legitimate national security risk from the Israelis, he could proceed with the proclamation regardless. The population of the predominantly Muslim countries on this list make up about 8 percent of the world's Muslim population.
"The question is, what are reasonable observers to think in that context?" "Ever" and "Refugees Welcome". The last time the court did that was for gay marriage arguments in 2015.
Fellow conservative Roberts questioned whether the president could be restricted from taking action on foreign policy emergencies, such as the civil war in Syria, if he is prevented from targeting specific countries.
Trump's own conservative appointee to the court, Neil Gorsuch, suggested that the lawsuits challenging the ban brought by Hawaii and others should not have been considered by courts in the first place. Its replacement was allowed to take partial effect, but expired in September.
The administration again appealed, and the president lashed out.
Francisco also said that because the ban does not affect the majority of the world's 2 billion Muslims, it can not be seen as targeting the religion.
Hearing the last arguments of its nine-month term Wednesday, the court took its first direct look at a policy that indefinitely bars more than 150 million people from entering the country.