The Fourth Circuit Court of Appeals on Monday heard oral arguments concerning the Trump administration’s second Refugee and Visa Order, also known as the Muslim ban. The case is one of many across the country challenging the order, which singles out individuals—including dual nationals, immigrants, and visa holders—from Iran, Libya, Somalia, Sudan, Syria, and Yemen for increased immigration scrutiny.

So far, the federal courts have temporarily blocked large parts of the order from taking effect. But those court orders are temporary. The tumultuous arguments on Monday suggested an appeals court uncomfortable with a president who openly campaigned on a promise to enact a Muslim ban—but one not completely convinced those challenging the administration had standing to bring a case at all.

And by the end of arguments, it wasn’t clear the Trump administration had enough votes from the appeals court judges to upend the order blocking enforcement of its ban. It was clear, however, that the issue of whether the bans were constitutional would eventually be headed up to the U.S. Supreme Court to resolve.

At least five federal courts have blocked the Trump administration’s travel ban. The case before the Fourth Circuit heard Monday is one of those cases. In March, a federal district court in Maryland sided with challengers and issued an injunction blocking the Trump administration from enforcing its ban while litigation challenging the order proceeds. The district court ruled the travel ban violates the U.S. Constitution’s Establishment Clause, because it effectively singles out members of the Muslim faith and individuals based on national origin for differential government treatment. The Trump administration appealed that decision, arguing the targeted countries represent reasonable national security threats, and that the order just so happens to have a disproportionate effect on Muslims.

The Fourth Circuit took the unusual step and heard the appeal immediately en banc, or as a whole, rather than first through a panel of judges, as is the norm.

As CNN’s Laura Jarrett reported, Allyson Kay Duncan, a George W. Bush nominee, and J. Harvie Wilkinson III, a Ronald Reagan nominee, both stepped aside from the case. Judges don’t have to give a reason why they recuse themselves, but in Wilkinson’s case, it could be that the acting attorney general who argued the case on the Trump administration’s behalf is his son-in-law, Jeffrey Wall.

Of the 13 judges that remained, ten are Democratic appointees. The Trump administration needs seven votes to overturn the injunction. That may sound like a sure bet given the numbers and presumed political leanings of those remaining judges. But on Monday the court appeared equally skeptical of both the challenge to the travel ban and the ban itself.

First up in the arguments was Wall, who was barely able to finish his introduction to the court when the judges began to press him to explain what would emerge as the key question in arguments: Is Trump’s revised travel ban a question of constitutional law or immigration law for the courts to resolve?

The Trump administration argues the courts should be following Kleindienst v. Mandel, a 1972 decision that ruled the attorney general had wide authority under immigration statutory law to deny people entry into the United States. The Mandel case holds that so long as the executive branch exercises its immigration authority on the basis of a “facially legitimate and bona fide reason,” the courts cannot examine its motives. There is one exception, however: If there is evidence that the government acted in bad faith, then courts can look into the reasoning behind the action.

The Justice Department argues the travel ban is “facially legitimate,” based on Trump’s determinations that the targeted countries, and travelers from and through them, pose heightened national security threats. The American Civil Liberties Union (ACLU), arguing on behalf of the challengers, counters the ban could not be facially legitimate because there is no constitutionally acceptable reason to target Muslims for heightened immigration scrutiny.

But when the federal district court blocked the ban in March, it didn’t rely on Mandel. Instead, it relied on a different line of cases, these under the Establishment Clause. According to the lower court, the Trump administration merely swapped out its promised and advertised “Muslim ban” for a list of targeted six Muslim-majority countries. But the order’s intent and effect was the same—to target Muslim travelers. The lower court used what’s known as the Lemon Test: a legal standard that, broadly speaking, judges government action targeting religion. Under the Lemon Test, government action must have a secular purpose: its principle or primary effect must not be to advance or inhibit religion, and the state cannot be excessively entangled in a particular religion. The Maryland district court relied on that test to find that the Trump administration can’t simply cite national security concerns as the basis for targeting a specific religious group for different treatment.

In other words, according to the lower court, Trump promised a Muslim ban, and he delivered a Muslim ban. And under the Lemon Test, those promises proved the ban unconstitutional.

Just what exactly Trump promised and delivered both during his campaign and days following his election, when the travel ban and its amended version were released, is at the heart of these legal challenges and untangling the Establishment Clause from immigration law issues. Trump did promise a Muslim ban. His advisers helped him craft one. And they bragged very publicly about doing so. That, attorneys for the ACLU argued, shows animus toward Muslim people and is evidence of an improper purpose in enacting the ban—to single out for disfavored treatment people of the Muslim faith or those TSA agents believe to be Muslim.

So far, federal courts have used those administrative statements to find evidence of improper animus behind Trump’s actions. In turn, the courts have used them as part of their basis for blocking enforcement, both under Mandel by holding, as the Ninth Circuit did, that there is no facially legitimate basis for the administration’s targeting of certain populations and under the Lemon Test to find the ban violated the Establishment Clause.

On Monday, the Fourth Circuit judges appeared reluctant to go so far as to hold that Trump’s statements could justify blocking the ban, concerned it created a subjective standard for courts to judge executive action and therefore further politicize the judiciary. The judges pressed Omar Jadwat from the ACLU for evidence from the language of the ban itself that it violated the Establishment Clause. The judges noted the travel ban makes no mention of religion, and included countries also found to be national security risks by the Obama administration. The judges pressed: Just how long can the “taint” of President’ Trump’s anti-Muslim statements haunt national security and immigration policy? Do we look into a politician’s statements while in college? What about the statements of his advisers?

Just how deep does the rot go?

Unfortunately, Jadwat didn’t give the court any good, direct answer as to how a plain read of the travel ban violates the Establishment Clause. Instead, Jadwat tried to direct the judges to “friend of the court” briefs and other outside evidence that refuted the administration’s targeting of the six countries affected by the ban. That didn’t seem to satisfy the court and the judges that were looking for a way to parse through the competing arguments of how far beyond the very words of the travel ban should courts go in determining its legality.

Jadwat also didn’t provide any clear answers to concerns the judges had over whether or not the ACLU’s clients even had the legal standing to bring the case in the first place. The Justice Department argued that organizations suing could show no actual injury from the travel ban; nor could the individual plaintiffs. The ACLU tried to counter that there is broad injury by targeting religious beliefs and specific national origins under the Establishment Clause, and pointed to one of the plaintiffs who is trying, so far unsuccessfully, to get his wife back into the country.

It’s not clear the judges agreed that the ACLU’s clients have standing to pursue this case. A ruling on this matter could have implications beyond the travel ban—it could also inadvertently limit who can and cannot challenge executive orders, such as the religious imposition order enacted last week. The Trump administration is clearly hoping that challenging the standing to sue is one way to legally insulate its orders, thereby shoring up power for the executive branch.

The judges’ tough questions for the ACLU on Monday don’t mean its challenge is doomed. And their skepticism, and at times palpable hostility, toward the administration’s actions in enacting the ban does not guarantee the order remains blocked. But it does show that the law around the ban is complicated, and that a clear-cut win on either side is not guaranteed.

On May 15, the Ninth Circuit Court of Appeals will hear arguments in a similar case brought by the State of Hawaii. A ruling in both cases is likely weeks away, if not longer. Should the courts issue conflicting opinions, the chances the issue goes before the Supreme Court increase dramatically.

That will likely leave the question of whether Trump’s Muslim ban is really a Muslim ban, or a legitimate exercise of presidential power to respond to a purported national security threat, up to the Supreme Court to decide.