The justices lobbed tough questions at both Solicitor General Noel Francisco (arguing for the government) and former acting solicitor general Neal K. Katyal (arguing on behalf of Hawaii and other organizations challenging the ban). Yet, according to reports from the New York Times and The Washington Post, Chief Justice John G. Roberts Jr. and Justice Anthony M. Kennedy, who some had hoped would join more liberal justices in opposing the ban, seemed skeptical of the challenge. Overall, the court seemed to favor the government’s argument.

The arguments:

Arguments for and against the ban fall along two axis, according to Vox. First, does the president have the legal authority to institute such a ban? Second, does it violate the First Amendment in terms of religious freedom?

Francisco, arguing for the government, made a case that the travel ban is for national security, and that the president does have legal authority for such an executive order for national security purposes through a provision in the Immigration and Nationality Act.

In terms of constitutionality, Francisco was asked a tough hypothetical by Justice Elena Kagan about whether a president who was a “vehement anti-Semite” could block travel from Israel. Francisco insisted that Trump’s third ban was not based on religion, but national security, and was signed after a “world-wide multi-agency review.”

Arguing against the ban, Katyal made the case that the president did not have the authority to impose the travel ban because Congress had already acted on this issue and passed laws. However, according to SCOTUSblog, Chief Justice Roberts did not seem convinced, and he worried about whether this would “entangle courts in second-guessing the president’s national-security determinations.” Justice Alito wondered, according to SCOTUSblog, if there could be a situation “in which the threat of terrorism could be so severe that the scheme that Congress enacted would be inadequate to deal with the problem?” Setting a precedent on the president’s powers and national security seemed to be of concern for several justices, according to Vox.

As for whether the ban was constitutional, Katyal argued that Trump’s previous statements showed an anti-Muslim bias, one that Katyal claimed was not disavowed after the campaign. The court will have to parse whether Trump’s previous statements impact the intent behind the ban.

In December of 2017, The 9th Circuit Court of Appeals blocked the ban by saying Trump “exceeded the authority that Congress had given him over immigration and had violated a part of the immigration laws barring discrimination in the issuance of visas,” according to the Times. It was also blocked by the 4th Circuit Court of Appeals in February, which said it violated the Constitution on the grounds of religious discrimination.

President Trump’s three travel bans:

The Trump administration has introduced three versions of a travel ban, and all three have been challenged in court. The first one in January 2017, just days after Trumps inauguration, banned travelers from seven Muslim-majority countries—Iraq, Syria, Iran, Libya, Somalia, Sudan and Yemen—for 90 days, halted the admission of Syrian refugees, and stalled the entire refugee program for 120 days. It was met with nation-wide protests and was eventually blocked by the courts.

The second ban, in March 2017, removed Iraq from the list of banned countries, but still banned nationals from Iran, Libya, Somalia, Sudan, Syria and Yemen from entering the United States for 90 days and all refugees for 120 days, CNN reported. This ban was blocked by a federal court in Maryland, which was upheld by the 4th Circuit of Appeals.

The third version of the executive order, signed in September, bars travelers from Iran, Libya, Syria, Yemen, Somalia, Chad, Venezuela (some government officials) and North Korea. Chad has since been taken off this list. Federal judges in Hawaii and Maryland, and on the 9th Circuit Court of Appeals and 4th Circuit Court of Appeals, upheld blocking the ban.

However, in December, the Supreme Court ruled that the third ban could go into effect while legal challenges were being heard. In February, the Supreme Court said it would hear oral arguments about the travel ban; its decision is expected in June.