The litigation in Jefferson County has lasted longer than most of the county’s residents have been alive. First filed by black plaintiffs in 1965, the case sought to desegregate the countywide school district, which serves suburban Birmingham and is today the state’s second-largest K-12 system. The court ordered the district to integrate, and has been supervising that process ever since.

The court’s order has not always been rigidly observed. Over time, Jefferson County’s whiter areas have splintered off and formed their own districts, a process that has accelerated since 2000. As a result, the racial demographics of the remainder of the county district have shifted dramatically—from approximately 75 percent white in 2000 to around 40 percent white today. The result has been that heavily black or single-race schools in the district—once the defining feature of Jim Crow-era segregation—have again become commonplace.

The most recent attempted defection was initiated by the residents of the small suburb of Gardendale. Its population of about 14,000 is 83 percent white. Because it is much whiter than the county district overall, Gardendale’s departure would increase the degree of racial concentration in the Jefferson County schools.

But something had changed. Judge Madeline Haikala, appointed by President Obama in 2013, was now presiding over the Jefferson County desegregation case. And Haikala has been, by all accounts, uncommonly sensitive to the problem of segregated schools. In writings from the bench, she has engaged with Alabama’s long history of segregation honestly and directly.

So when Gardendale sought permission to split from the Jefferson County district, it found itself embroiled in a legal showdown with integration advocates who opposed secession, overseen by an unsympathetic judge.

The advocates’ argument was straightforward: A longstanding rule created by the Supreme Court in 1972 holds that schools under a desegregation order cannot split away and form a splinter district if doing so would undermine the process of desegregation. The advocates also contended that Gardendale’s proposed secession was not innocent or well-intentioned—it was motivated by racial animus.

Judge Haikala agreed with the desegregation advocates on both counts. In a 190-page opinion summarizing the history of civil rights in Jefferson County schools, she called elements of the secession campaign “deplorable.” She agreed that it was motivated by a desire to discriminate. And then, to the advocates’ dismay, she approved a plan to allow Gardendale’s secession to go forward anyway.

To understand why Judge Haikala did what she did, it’s necessary to understand the basic structure of school-desegregation law in the United States. Brown v. Board of Education, with its affirmation in 1954 that “separate educational facilities are inherently unequal,” is easily the most famous desegregation case. But much of the hard work of actually integrating schools came later, starting in earnest with a 1968 Supreme Court case called Green v. County School Board of New Kent County, which laid out specific standards for that process. Out of Green and the many cases that followed it, the Supreme Court built a complex and versatile set of rules for desegregating schools. There is nothing else quite like it in American jurisprudence: an elaborate body of Supreme Court precedent, all focused on accomplishing one narrow task.