NEW YORK (Reuters) - A U.S. appeals court is weighing arguments for and against President Donald Trump’s temporary travel ban, but its decision this week may not yet answer the underlying legal questions being raised in the fast-moving case.

The James R. Browning U.S. Court of Appeals Building, home of the 9th U.S. Circuit Court of Appeals, is pictured in San Francisco, California February 7, 2017. REUTERS/Noah Berger

The 9th U.S. Circuit Court of Appeals in San Francisco is expected to rule only on the narrow question of whether a lower court’s emergency halt to an executive order by Trump was justified. Trump signed the order on Jan. 27 barring citizens from seven Muslim-majority countries for 90 days and halted all refugee entries for four months.

The appeals court has several options. It could kick the case back to lower court judge James Robart in Seattle, saying it is premature for them to make a ruling before he has had a chance to consider all the evidence. Robart stopped Trump’s order just a week after he issued it and before all the arguments had been developed on both sides.

Or the panel of three appellate judges could side with the government and find halting the order was harmful to national security, reinstating it while the case continues.

Their decision is “one step in what will be a long, historic case,” Stephen Yale-Loehr, a professor at Cornell University Law School who specializes in immigration. Ultimately, the case is likely to end up in the U.S. Supreme Court, legal experts said.

The case is the first serious test of executive authority since Trump became president on Jan. 20, and legal experts said there were three main issues at play for the judiciary.

The broad questions in the case are whether the states have the right to challenge federal immigration laws, how much power the court has to question the president’s national security decisions, and if the order discriminates against Muslims.

Washington state filed the original lawsuit, claiming it was hurt by the ban when students and faculty from state-run universities and corporate employees were stranded overseas.

Trump administration lawyer August Flentje argued at an appeals court hearing on Tuesday that the states lack “standing” to sue the federal government over immigration law, but his arguments were questioned by the judges.

NATIONAL SECURITY

If the court decides the states are allowed to bring the case, the next major question is about the limits of the president’s power.

“Historically courts have been exceedingly deferential to governmental actions in the immigration area,” said Jonathan Adler, a Case Western Reserve University School of Law professor. Though, he added, “the way they carried it out understandably makes some people, and perhaps some courts, uneasy with applying the traditional rules.”

Trump issued the order late on a Friday and caused chaos at airports as officials struggled to quickly change procedures.

At Tuesday’s hearing, Judge Richard Clifton, an appointee of Republican president George W. Bush and Judge William Canby, an appointee of Democratic president Jimmy Carter, pushed the government to explain what would happen if Trump simply decided to ban all Muslims from entering the United States. “Would anybody be able to challenge that?” Canby asked.

Flentje emphasized that the order did not ban Muslims. He said the president made a determination about immigration policy based on a legitimate assessment of risk.

The government has said its order is grounded in a law passed by congress that allows the president to suspend the entry of “any class of aliens” that he deems “would be detrimental to the interests of the United States.”

When asked by the third judge - Michelle Friedland, appointed by Democrat Barack Obama - if that meant the president’s decisions are “unreviewable” Flentje, after a pause, answered “yes.” When pressed, Flentje acknowledged, however, that constitutional concerns had been raised about the order.

RELIGIOUS DISCRIMINATION

One of the main concerns is allegations by the states, civil rights groups, some lawmakers and citizens that the order discriminates in violation of the constitution’s First Amendment, which prohibits favoring one religion over another.

The judges will have to decide whether to look exclusively at the actual text of the president’s order, which does not mention any particular religion, or consider outside comments by Trump and his team to discern their intent.

Washington state’s attorney Noah Purcell told the hearing that even though the lawsuit is at an early stage, the amount of evidence that Trump intended to discriminate against Muslims is “remarkable.” It cited Trump’s campaign promises of a “total and complete shutdown of Muslims entering the United States.”

In a tweet on Monday night, Trump said “the threat from radical Islamic terrorism is very real” urging the courts to act quickly.

Government lawyer Flentje countered Purcell by saying there was danger in second guessing Trump’s decision-making about U.S. security “based on some newspaper articles.”

Clifton asked about statements on Fox News by Trump adviser Rudolph Giuliani, former New York mayor and former prosecutor, that Trump had asked him to figure out how to make a Muslim ban legal.

“Do you deny that in fact the statements attributed to then candidate Trump and to his political advisers and most recently Mr. Giuliani?” Clifton asked. “Either those types of statements were made or not,” said Clifton. “If they were made it is potential evidence.”

(Reporting by Mica Rosenberg in New York; Additional reporting by Lawrence Hurley in Washington and Nathan Layne in New York; Editing by Noeleen Walder and Grant McCool)