During Anthony Kennedy’s long reign as the Supreme Court’s swing vote, advocates perfected the art of “the Kennedy brief”: a legal argument designed to win his support by rhapsodizing about “dignity” and “liberty.” While the Kennedy brief went extinct upon his retirement, it may now be replaced by the Gorsuch brief, which replaces florid encomia to freedom with highly technical textualist arguments. The American Civil Liberties Union tested this strategy in a major immigrant-detention case this week. Gorsuch’s questions indicate it just might have worked.

Wednesday’s case, Nielsen v. Preap, revolves around a statute that requires the mandatory detention, without bond, of certain unauthorized immigrants. This law states that the secretary of Homeland Security “shall take into custody” a noncitizen who has committed certain crimes “when the alien is released” from criminal custody. The Trump administration claims that, under this provision, it may arrest and detain an unauthorized immigrant indefinitely a day, a month, a decade, or even a half-century after she’s been released from custody. The ACLU argues the government must detain these individuals immediately upon their release. If it fails to do so, the ACLU asserts, the government may still detain them at some point down the road, but it must grant them the same bond hearings that other individuals in immigrant detention receive.

Preap thus comes down to the meaning of when. That makes it an ideal case for Gorsuch. As a proud textualist, the justice purports to focus on each word in a statute, focusing on the plain meaning rather than legislative intent. That task often requires an extremely careful reading of each sentence, word, even punctuation mark in the law at issue.

In theory, textualism should sometimes lead to liberal results. But past conservative justices have abandoned textualist interpretations when they might produce a progressive outcome. Preap will determine whether Gorsuch adheres to a principled jurisprudence when textualism pushes him to the left. If he does, the Gorsuch brief will become a cottage industry: In every statutory interpretation case, progressive attorneys will provide the justice with complex grammatical analyses that scrutinize every subsection and comma to bolster their reading of the law.

If Gorsuch follows his textualist instincts, he should reach a progressive result.

That brings us back to when. The Trump administration believes that in this statute, this word grants the government an open-ended option to lock up this class of immigrants at any point. By contrast, the ACLU believes it conveys a sense of “immediacy.” It says the purpose of the statute was to prevent a “gap” between an unauthorized immigrant’s release from criminal custody and his transfer to immigrant detention. (The congressional record confirms that lawmakers had this goal in mind.) The 1st U.S. Circuit Court of Appeals and the 9th U.S. Circuit Court of Appeals have issued rulings that agree with the ACLU’s interpretation, while four other courts of appeals have sided with the government’s reading. Now the Supreme Court will resolve the circuit split.

In the Kennedy era, the ACLU’s brief likely would’ve focused on this statute’s grave threat to liberty and its affront to the dignity of unauthorized immigrants who’ve spent years building lives in their communities, only to be snatched up by the government and held without bond. With Kennedy off the bench and Gorsuch the ACLU’s most gettable vote, the group’s Preap brief deconstructs the statute’s language, urging the court to apply “the statute’s literal terms” and reject the government’s “contrary interpretation,” which “turns the plain language” and “structure” of the law “upside down.”

“The government’s interpretation,” the brief concludes, “eviscerates the very duty that Congress sought to impose.” If “when … released” means only “at any time after” release, then the law’s detention mandate “becomes, in effect, discretionary.” Should the Supreme Court accept the government’s view, it would essentially rewrite the statute in defiance of congressional intent.

At oral arguments, Gorsuch followed the ACLU’s lead, immediately latching onto the strange consequences of the government’s reading. He asked Zachary Tripp, a Justice Department attorney, if the government should seize an unauthorized immigrant 30 years after his release—even if “was aware of him the entire time and chose not to act.”

“Is there any limit on the government’s power?” Gorsuch asked Tripp. Eventually, Tripp admitted that, no, there isn’t: Under his argument, the government can ignore an unauthorized immigrant for decades, then detain him, without bond, on a whim. The justice seemed troubled. No limit? “Fifty years” after an unauthorized immigrant commits “a minor crime, you say, yes, the government must come and arrest him?” he asked.

Gorsuch, though, had equally tough questions for ACLU deputy legal director Cecillia Wang. He focused on another provision of the statute that states that the government “may release” an unauthorized immigrant taken into custody under the law “only if … necessary” for witness protection. Reading these sections together, Gorsuch asked, doesn’t it seem as if the government must keep these immigrants in custody no matter when they were detained—unless they’re placed in witness protection? In other words, doesn’t this provision clarify any ambiguity by stating that, regardless of when these immigrants are detained, they can only be released for one specific reason?

Wang was ready with a retort. “Let me give you a hypothetical example that tracks this statute,” she said:

I might tell you in a two-paragraph instruction. [Paragraph] one: Harvest the grapes in vineyards A, B, and C when they ripen. Paragraph two: Make the wine from the grapes described in Paragraph 1. The grapes refer to both the temporal component—I want you to harvest them when they’re ripe, not when they’re overripe, not when they’re underripe—and it’s from those three vineyards.

The idea here is that when Wang says “make the wine from the grapes,” she isn’t referring to all of the grapes—whether or not they’re ripe. She’s referring to a subset of grapes, the ripe ones. Similarly, when the law says that the government “may release” certain immigrants only for witness protection, it isn’t referring to all of the immigrants described in the statute. It’s referring to the immigrants who were detained when they were released from criminal custody, as the statute commands. Unauthorized immigrants whom the government picked up after their release can still receive a bond hearing, like almost all others.

Gorsuch was impressed. “It’s a neat example,” he told Wang. “I commend you. Well done.” But he noted that “I’m not sure I buy it,” and the two went back-and-forth over the meaning of the “adverbial phrase.” It’s not clear whether Wang ultimately persuaded Gorsuch, but he seemed genuinely open to her argument, at one point even asking her to “help me out.” If he does wind up agreeing with Wang, it could be the second time he has sided with the liberals in a 5–4 immigrant-detention case. And it would mark a stark contrast with Justice Brett Kavanaugh, who appeared highly skeptical of Wang’s position.

On Thursday, I asked Wang whether she had catered her argument to Gorsuch, a noted grammarian and devoted textualist. She told me she always believed she should win “under the words that Congress wrote.” The ACLU “started with the plain text of the statute,” Wang said, and “that’s just how the arguments came together. It’s common sense: When means when.” The government’s position, by comparison, is “a really tortured interpretation” that writes a key phrase out of the statute.

If Gorsuch follows his textualist instincts, he should reach a progressive result that would grant bond hearings to thousands of unauthorized immigrants. But even if he sides with the conservatives, the ACLU is onto something here. Gorsuch’s eagerness to grasp Wang’s textualist interpretation provides more evidence that the justice isn’t just another law-and-order hard-liner. With enough grammatical precision, liberal advocates might occasionally lead him to results that the Trump administration despises. The era of the Gorsuch brief has arrived.

Update, Oct. 11, 2018: This piece has been updated to specify that the statute affects unauthorized immigrants.