Monday, January 27, marked the three-year anniversary of President Trump’s executive order on Protecting the Nation from Foreign Terrorist Entry into the United States, commonly referred to as the “Muslim travel ban.” Here, Professor Shirin Sinnar, an expert in national security and civil rights, shares her views on the current version of the order, challenges to it, and the administration’s potential plans to expand it.

The ban has faded a bit from mainstream headlines recently. Can you remind us of the key points of the executive order and the people it covers?

The travel ban in effect today comes from a proclamation issued by President Trump in September 2017, after federal courts had blocked two earlier versions of the ban. The current version bars some or all people from seven, mostly Muslim-majority countries, from entering the United States. President Trump first advocated for such a ban as a presidential candidate, when he called for a “total and complete shutdown of Muslims entering the United States.”

The ban has had dramatic effects. For instance, from 2016 to 2018, the number of visas issued to people from Iran, Libya, Somalia, Syria, and Yemen dropped by eighty percent. This includes separating close family members. According to the Cato Institute, in little over a year, the ban separated over 9,000 spouses and adopted minor children from joining U.S. citizen spouses or parents in the United States.

The travel ban also affects colleges and universities. For instance, visa denials and delays have prevented many Iranian scientists and students from attending research conferences or studying in the United States. In addition, international awareness of the travel ban and other new restrictions has encouraged people to go elsewhere for study, business, and tourism.

What was the main rationale for the order?

The proclamation stated that the countries it targeted had inadequate procedures to establish the identity of their citizens, failed to share sufficient information with the United States regarding their citizens’ security risks, or had other security “risk factors.” It described the entry ban as a mechanism to compel countries to improve their vetting procedures or security cooperation with the United States.

More than 55 former national security officials, including former secretaries of state, CIA directors, and other top intelligence officials from both Democratic and Republican administrations, submitted an amicus brief to the Supreme Court calling the travel ban unnecessary and counterproductive for U.S. national security.

More recently, the administration has floated the idea of expanding the ban to possibly include countries from Europe, Africa, and Asia. Can you talk about the legality of that?

We know little about the potential new ban, including which countries it might include and what rationales the administration might invoke. A new travel ban would likely be challenged as unconstitutional discrimination under the Equal Protection Clause and First Amendment, given the President’s persistent anti-Muslim and racist remarks, often in the immigration context. The President’s reported screed against migration from “shithole countries” (and preference for immigration from Norway) and his calls for U.S. congresswomen of color to go back to their “broken and crime infested” countries are examples. Recent revelations that Stephen Miller, the president’s chief immigration advisor, appears to have intellectual links to white nationalism, further supports the idea that animus against non-white immigrants partly motivates the administration’s restrictionist immigration policies.

Nonetheless, the Supreme Court upheld the travel ban in a 5-4 decision that set aside the president’s anti-Muslim statements because, the Court said, it was possible to discern a national security justification for the policy. Under the highly deferential standard of review applied in Trump v. Hawaii, it’s hard to see how this Supreme Court would deem similar bans discriminatory so long as the government goes through the motions of supplying national security or foreign policy reasons for the ban.

In June 2018, the Supreme Court upheld President Trump’s ban, rejecting findings from lower courts that deemed the ban unconstitutional. Was that the last word—or is it still being challenged? Can you talk about other cases working their way through the courts? How is the law developing?

A number of lawsuits continue to challenge the travel ban. On Tuesday, January 28, the Fourth Circuit will hear oral arguments in International Refugee Assistance Project v. Trump, a constitutional challenge to the travel ban which the lower court allowed to move forward. The government contends that the plaintiffs are simply trying to re-litigate Trump v. Hawaii with arguments the Supreme Court already rejected. The challengers respond that, in that decision, the Supreme Court only overturned a preliminary injunction against the ban rather than decide the ultimate merits of the case. They argue that, if the case moves forward, discovery would allow them to show that the ban didn’t actually have a “rational basis.” For instance, further information might show that the multi-agency decision-making process that led to the ban was actually a sham, or that there are substantial roadblocks for individuals to get a hardship waiver from the ban.

In a separate case in the Northern District of California, Emami v. Nielsen, plaintiffs claim that federal agencies are violating their own rules in administering the waiver program. They argue that the government has, at times, barred visa applicants from the banned countries from showing they’re eligible for a waiver or encouraged consular officials to issue blanket denials. (In September, administration officials reported that 10% of visa applicants had received waivers, about half of those within the prior two months).

What is the role of Congress in this?

Part of the problem behind the travel bans is that Congress has, in fact, delegated broad power to the president to exclude people whose entry he finds to be “detrimental to the interests of the United States.” Congress passed that provision in an infamous 1952 immigration law designed to preserve racist national origin quotas.

Although Congress later eliminated the national origin quota system and forbade race and nationality discrimination in the issuance of immigrant visas, the Supreme Court in Trump v. Hawaii held that the prohibition on discrimination didn’t apply to the president’s authority to deny entry.

The result of the Court’s statutory interpretation and toothless constitutional review is an astonishingly broad interpretation of the president’s power to restrict immigration. But Congress can curb this power. For instance, last April, Senator Christopher Coons and Representative Judy Chu introduced the National Origin-Based Antidiscrimination for Nonimmigrants Act (NO BAN Act) to limit the president’s exclusion power to cases where the Secretary of State concludes that entry should be suspended in response to defined circumstances and on the basis of “credible facts.”

The broader point is that, in immigration and other contexts, Congress has often conferred wide authority to the executive to act in the name of national security or national emergencies. Whether it’s the travel ban, steel and aluminum tariffs, or the building of the border wall, recent policies show the consequences of legislative reliance on executive good faith and self-restraint.

Shirin Sinnar is Professor of Law and the John A. Wilson Faculty Scholar at Stanford Law School. Her scholarship focuses on the role of institutions, including courts and executive branch agencies, in protecting individual rights and democratic values in the national security context.