On Tuesday, Justice Neil Gorsuch voted with the Supreme Court’s liberals to strike down the key provision of a statute that allows the expulsion of certain noncitizens. The ruling in Sessions v. Dimaya was notable for throwing a wrench into the federal government’s deportation regime. It was also groundbreaking for another, less obvious reason: It marked the first time Justice Ruth Bader Ginsburg assigned a majority opinion in her nearly 25 years on the high court.

This milestone is long overdue. Justices receive the power to assign opinions as they gain seniority: The most senior justice in the majority gets to assign the opinion of the court, an important task with ramifications for the outcome of the case. Seniority is determined by years of service, though the chief justice is always considered the most senior. That means Ginsburg is currently the fourth most senior justice, following Chief Justice John Roberts, Justice Anthony Kennedy, and Justice Clarence Thomas.

Ginsburg became the most senior liberal justice after Justice John Paul Stevens retired in 2010. Yet whenever she’s found herself in the majority in a 5–4 decision, another justice has been able to claim seniority. Occasionally, Roberts or Thomas joins the liberal justices. Kennedy, though, is usually the swing vote, and he likes to assign landmark progressive decisions—like the marriage equality rulings—to himself. If Justice Samuel Alito had given the liberals a fifth vote since Stevens’ retirement, Ginsburg could’ve assigned the opinion. But in his 12 years on the bench, Alito has not once joined the liberals in a 5–4 ruling.

When Gorsuch cast his vote in Dimaya, he gave Ginsburg a novel opportunity—the power to assign the opinion of the court. And not just any opinion but a hugely consequential decision strengthening the Due Process Clause’s guarantee against vague legislation. Ginsburg gave that task to Justice Elena Kagan, which is no surprise. Kagan is a brilliant writer who can thread the jurisprudential needle with eloquence and wit. She’s a canny strategist with moderate instincts and a knack for coalition-building. Kennedy and Thomas have, respectively, assigned Kagan opinions in big cases involving juvenile life without parole and racial gerrymandering. She hit both out of the park, pushing the law leftward without alienating her right-leaning colleagues.

When writing a majority opinion, a justice isn’t merely speaking for herself; she’s speaking for “the court,” effectively announcing the law of the land. When writing for a slim majority, she must often incorporate qualifications and concessions from her colleagues so she can retain their votes. We don’t yet know whether Kagan and Gorsuch wrangled over the language of the opinion, though such disputation wouldn’t be out of character for either. What we do know is that Kagan managed to hold onto Gorsuch’s vote, drawing this punctilious, idiosyncratic justice’s support for the bulk of her opinion.

Ginsburg had another plausible option when assigning Dimaya: She could’ve given it to Gorsuch. In 5–4 decisions, the senior-most justice sometimes assigns the majority opinion to the colleague most likely to defect, hoping to solidify his or her vote. There are a few reasons why Ginsburg might not have deployed that strategy here. First, Gorsuch’s reasoning did differ a bit from that of his liberal colleagues; if that distinction became clear at conference, when the justices discuss cases and cast votes, Ginsburg would’ve known to avoid handing him the majority opinion. Second, and relatedly, Ginsburg may have worried that Gorsuch would try to slip in language that could hurt progressive jurisprudence in other areas. Indeed, he wound up doing exactly that in his separate concurrence. As usual, Ginsburg made the right call.

There’s another path-breaking dimension to Ginsburg’s Dimaya assignment that the justice would probably appreciate: According to Adam Feldman, creator of Empirical SCOTUS, it marks just the sixth time that a female justice has been able to assign a majority opinion. The first woman on the court, Justice Sandra Day O’Connor, almost always found herself in the majority with either Stevens or Chief Justice William Rehnquist, and thus was only able to assign the majority opinion five times during her nearly quarter-century tenure. Of those cases, she assigned two to herself and two to Ginsburg, perhaps in a bid to rectify the grave gender disparity in case assignments. (Per Feldman, Ginsburg has now written 199 majority opinions.)

No one expects Gorsuch to join the liberals regularly in contested cases. And it’s worth noting that if Merrick Garland sat in the seat Gorsuch now occupies, Ginsburg would’ve routinely had the authority to perform this role, a privilege of which she was unjustly robbed. But Gorsuch has already demonstrated more ideological independence than Alito, and he seems poised to swing left at least once more this term. That means Ginsburg should have more opportunities to assign opinions—and further guide the direction of the law—in the twilight of her tenure.