Now that the U.S. Supreme Court has been asked to consider President Donald Trump’s travel ban, there’s one word you need to focus on: animus.

In legalese, it means an illegitimate prejudice. It was the key to the lower court decisions freezing the ban. And it’s one of the master concepts in swing voter Justice Anthony Kennedy’s jurisprudence. You might even say that animus is the opposite side of the coin to Kennedy’s other great master concept, dignity.

If Kennedy reads Trump’s executive order temporarily blocking immigration from six predominantly Muslim countries as an exercise of anti-Muslim animus, the ban will fall at the court. And that seems highly likely, given that it would be difficult for the justice to downplay Trump’s prejudice without betraying his own legacy.

The origins of the term animus go back at least a couple of hundred years. In Latin, animus just means the soul. By extension, having an “animus” to do something came to mean an intent to do so. Many phrases in legal Latin use the word neutrally to mean an intention that could be good, evil or indifferent.

But gradually,  the legal word for “intent” came to mean something like hostility. This usage was probably influenced by the English word “animosity,” which itself was originally neutral and came to mean hostility as early as the 17th century.

In constitutional law, animus began its path to contemporary importance in Kennedy’s 1996 landmark gay-rights opinion in Romer v. Evans. Kennedy wanted to use the equal protection clause of the Constitution strike down an amendment to the Colorado state constitution adopted by referendum. On its face, the amendment said the state’s legislature and cities couldn’t adopt anti-discrimination laws to protect gay people.

Before the Romer decision, the standard way to strike down laws as violating equal protection was to begin by saying that those laws suspiciously burdened a class of people who could be characterized as a “discrete and insular minority,” classically blacks. Kennedy didn’t want to say that gay people should be considered a discrete and insular minority.

The legal alternative was that, in order to strike down the law, Kennedy had to show that the law wasn’t rational. That’s usually a pretty low bar, because almost any law can be said to have some rational basis.

Here Kennedy got creative. He wrote that the Colorado amendment’s “sheer breadth is so discontinuous with the reasons offered for it that the amendment seems inexplicable by anything but animus toward the class that it affects.”

Given the presence of animus, Kennedy concluded, the amendment lacked “a rational relationship to legitimate state interests.” It was therefore unconstitutional.

This was a quiet constitutional revolution, as Justice Antonin Scalia noticed in a searing dissent that famously accused Kennedy of confusing a culture war over homosexuality with a “fit of spite” against gay people.

Scalia went on to argue that animus didn’t violate the Constitution. “Of course it is our moral heritage that one should not hate any human being or class of human beings,” he wrote acerbically. “But I had thought that one could consider certain conduct reprehensible – murder, for example, or polygamy, or cruelty to animals – and could exhibit even ‘animus’ toward such conduct.”

From the Romer precedent, animus began to make its way into other parts of constitutional doctrine, including religious liberty. In 1993, before Romer, Kennedy had written an important decision called  Church of Lukumi Babalu Aye v. City of Hialeah. In that case, he said, “the free exercise clause protects against governmental hostility which is masked, as well as overt.” Kennedy had then used the word “hostility.” But subsequent applications of the Lukumi principle have substituted the word “animus,” which seems to have much the same meaning.

The courts that froze the travel ban have often relied on the Lukumi precedent while using “animus.”

For Kennedy, animus became a master concept in his 2013 gay-marriage decision, U.S. v. Windsor, which struck down the federal Defense of Marriage Act. There animus came to be paired with Kennedy’s concept of dignity.

In the Windsor case, Kennedy wrote that DOMA sought to injure gay couples who were allowed to marry by state law. The law was therefore motivated by “improper animus or purpose,” Kennedy said, citing his own Romer decision in support. (Scalia, on cue, responded that Congress was motivated not by “animus” but by “stabilizing prudence” in the presence of conflicting state laws on marriage.)

And in the Windsor case, Kennedy also famously made the point, repeated two years later in Obergefell v. Hodges, the right-to-gay-marriage case, that allowing a couple to marry conferred dignity on the partners. Taking away the right to marry therefore produced “injury and indignity.”

By implication, then, to treat a group of people with unconstitutional animus is to deny them dignity — which adds up to a constitutional violation.

Presumably, at least some of the Supreme Court’s conservatives, channeling Scalia, will want to say that Trump’s executive order on its face does nothing to demean Muslims. But Kennedy will be under enormous pressure to pay attention to Trump’s public statements before and after the election, statements that led the lower courts to say that the travel ban was the product of anti-Muslim animus.

There remain technical questions of whether the ban violates the Constitution’s establishment clause, the free exercise clause or even the equal protection clause. But the bottom line for Kennedy is that if he ignores the animus issue that the lower courts emphasized, he runs the risk of undercutting his legacy.

For what it’s worth, I find it almost impossible to believe that Kennedy, at 80, would want to sign an opinion closing his eyes to animus, which he himself did so much to make into a constitutional touchstone. That should be enough to make sure the travel ban doesn’t take effect.

This column does not necessarily reflect the opinion of the editorial board or Bloomberg LP and its owners.

Noah Feldman is a Bloomberg View columnist. He is a professor of constitutional and international law at Harvard University and was a clerk to U.S. Supreme Court Justice David Souter. His seven books include “The Three Lives of James Madison: Genius, Partisan, President” and “Cool War: The Future of Global Competition.”

  1. I think over the course of the 19th century, but that’s not a historically sound conclusion, just an impression.

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Photo Credit: President Donald Trump speaks at a rally March 15, 2017, in Nashville, Tennessee. Mark Humphrey / Associated Press