Mass incarceration cripples families and communities, perpetuates poverty, recreates conditions for crime, and institutionalizes a form of racial control. As a result about one in four American adults (65 million) now have a criminal record.

Consider that for a moment—even in the context of historically disastrous periods of American history. One quarter is also the proportion of Americans unemployed in 1933, at the height of the Great Depression, which included the “worst month for joblessness in the history of the United States.” It’s the same proportion as the casualty rate for Civil War soldiers. It’s almost three times the percent of Americans enlisted in World War II.

The issue has been slow to enter public discourse, perhaps because the most affected populations are also the most marginalized. From scenes of armored vehicles and snipers in Ferguson to the totalitarianism of the prison system as presented in Orange is the New Black, that may slowly be changing. Various advocacy groups are organizing movements, some in Congress see an opportunity for bipartisan reform, and litigators continue to seek incremental victories against practices like stop-and-frisk.

But these efforts will not be enough to significantly affect a problem of this scale—at least not alone. Like the critical junctures of past generations, the Civil War or the Great Depression, this is a problem that requires presidential leadership. As the executive, Obama wields straightforward and fundamental power to reduce the scale of mass incarceration; as president, and in particular as a black male president, his ability to address the racial dimension of the system is significantly less clear. Nonetheless, with Attorney General Eric Holder stepping down, the Democrats' loss of the Senate in the midterms, and and the end of Obama’s presidency looming ever closer, the time and space for action continue to shrink and all signs point in one direction.

It isn’t that presidential action is necessarily a great choice. It’s that other options are structurally impossible or temporarily unavailable. For most policy issues, change can come about three ways, besides from the executive: popular movement, Congress, or legal challenge in the courts. The nature of mass incarceration in the U.S., though, prevents serious change through these alternative routes—even despite some recent signs for hope.

The protest surrounding Michael Brown’s shooting might seem like a chance for reform, but social and legal structures make popular movements against mass incarceration difficult. The populations most disadvantaged by the current system are traditionally the most marginalized, poor, and minority communities. They have the lowest social capital, little wealth for advocacy, and least access to political elites. Felon disenfranchisement stifles an electoral threat and substantially affects political outcomes. Parole conditions prevent felons from associating (read: organizing) with one another. The risk of arrest dissuades civil disobedience. Moreover, discrimination in hiring, continued state bans on SNAP and TANF eligibility, and abusive civil forfeiture practices mean that those who have gone through the justice system tend to lack financial means for effective advocacy. To compound issues, there are opposing forces with money to spare—the Corrections Corporation of America for example, whose business model is increased incarceration, recently paid more than $250,000 just to participate in the Republican Governors Association proceedings and has spent almost $14 million on lobbying in the last eight years. By contrast, Families Against Mandatory Minimums, a leading reform advocacy organization, only spent $80,000 on federal lobbying in 2014.