It’s going to take a lot more than a Supreme Court decision to reform our appalling prisons.

Today the United States is the world’s warden, incarcerating more people than any other country. With just 5 percent of the world’s population, it has 25 percent of its prisoners. Since the 1970s, the United States has built the largest penal system in the world to accommodate a sixfold increase in its inmate population. But what happens behind its prison walls generally remains far removed from public consciousness. In this context, the Supreme Court’s landmark decision in Brown v. Plata last month, which declared that the degrading and inhumane conditions in California’s grossly overcrowded prisons are unconstitutional, was an exceptional moment when the prison wall was briefly breached.

Of course, Brown v. Plata does not mark the beginning of the end of mass incarceration in the United States, nor of the abusive conditions that proliferate in U.S. prisons and jails. Unlike the landmark prisoners’ rights cases of the 1960s and 1970s, this decision is unlikely to spur many successful copycat lawsuits to impose prison population caps and revitalize the courts as a major forum to challenge abusive prison conditions. The Prison Litigation Reform Act (PLRA), enacted by Congress in 1996 to greatly constrict prisoners’ access to the courts and to reduce the judiciary’s role in monitoring the penal system, continues to present formidable obstacles for inmates seeking to challenge their conditions of confinement. For those few cases that successfully navigate the PLRA and make it into the courts, the legal process is long and protracted. Remarkably, the U.S. prison and jail population has more than doubled since 1990, the year that one of the two lawsuits eventually consolidated in Brown v. Plata was initially filed.

Moreover, Brown v. Plata is not even likely to spur major reductions in California’s inmate population any time soon. This is because the Supreme Court conceded great latitude to the Golden State in how to reduce overcrowding in its prisons and by when. State officials could choose to release some prisoners early. But they could also address the population cap affirmed by the Supreme Court by sending more prisoners to out-of state penal facilities or to county jails in California. Or California could simply build more prisons.

So why, then, is this a landmark decision with enormous implications for the future course of penal policy reform in the United States? More so than many other Supreme Court decisions, Brown v. Plata was as much a political statement as a legal one. It did not render the PLRA restrictions on challenging the conditions of confinement through the courts any less arduous. But it did pry open some important political space that could help incubate political solutions to the problem of mass incarceration in the United States.

The first way in which the Court opened up some political space for prison reform was by making the abhorrent conditions in California’s prisons strikingly visible. In the nineteenth century, prisons opened their doors to the public and were popular destinations for gawking domestic and foreign tourists. In the 1960s and early 1970s, prison memoirs and accounts of life behind bars regularly turned up on best-seller lists. Today, however, the U.S. penal system is distinctive not only because of its huge size, but also because of its relative invisibility—leaving aside television shows like Oz, which contribute to a grossly distorted view of what is at stake in mass incarceration. The hundreds of prisons and jails that dot rural America and the desolate outskirts of cities, the 2.4 million men and women currently locked up, the 750,000 former offenders released from prison each year with stunted life chances, and the struggles of the millions of children with an incarcerated mother or father tend to leave little trace on the wider public consciousness.