First there was one, then there were two—both blocked by lower federal courts. And finally, before the Supreme Court could rule on the second, came Donald Trump's Muslim ban 3.0, which the high court will hear oral arguments on this Wednesday.
Frankly, Trump has a lot of presidential precedent pointing in his favor in Trump v. Hawaii. The executive branch has inherent constitutional authority over foreign policy matters and a good deal of latitude in determining who should and shouldn't be entering the country based on national security considerations. Additionally, the Supreme Court in December blocked a lower court's injunction on Trump’s Muslim ban 2.0, suggesting a majority of the justices believed Trump would have won the case if they had had the chance to weigh its merits.
All that being said, Trump isn't just any pr*sident. He rode to office blatantly promising to ban Muslims from entering the country, which many opponents—including some conservative religious organizations—view as a clear violation of First Amendment protections against religious discrimination. That was the rationale behind the Fourth Circuit Court of Appeals' ruling against the ban.
Additionally, the court will review whether the policy was a product of Trump's own animus against Muslims, and Trump's ill-considered prolific tweeting could become pivotal to that discussion. The Washington Post writes:
Hawaii’s brief, by Washington lawyer Neal K. Katyal, cites not only Trump’s campaign comments, but also his actions as president, including the time he retweeted “three anti-Muslim propaganda videos” from a widely condemned far-right British organization.
This led to a response by the solicitor general of the United States to the justices of the Supreme Court that could have been written only in this era, about this chief executive:
“The president’s retweets do not address the meaning of the proclamation at all.” [...]
If the president’s comments and tweets were not a factor, many legal experts said, the court would be likely to extend the deference to the political branches it has shown in the past when considering issues of immigration and national security.
Along with weighing First Amendment protections and Trump's motives, the justices will also consider what role the courts even have in regulating the executive branch on such an immigration order.
The Muslim ban 3.0 blocks entry into the country from Iran, Libya, Somalia, Syria, and Yemen, as well as certain visitors from North Korea and Venezuela. But Hawaii's legal challenge only covers the first five countries (Chad, originally included in the ban, was dropped by the administration earlier this month.)
The libertarian Cato Institute says its research leads to the conclusion that the ban is based more on discrimination than protection.
“Not a single person from these countries has killed anyone in a terrorist attack in the United States in over four decades,” the brief stated. “Nationals of the designated countries have also been much less likely to commit other serious crimes than U.S.-born persons or other foreign nationals.”
That means both a high-profile conservative think tank and the conservative U.S. Conference of Catholic Bishops submitted “friend of the court” briefs urging the justices to strike down the ban.