California is suffering record-breaking wildfires as the Mendocino Complex, Carr, and Ferguson fires continue. But to combat the flames, the state is turning to a controversial practice: prison labor.

The California Department of Corrections and Rehabilitation (CDCR) recently boasted about the use of prison labor for firefighting on Twitter: “Today, more than 2,000 volunteer inmate firefighters, including 58 youth offenders, are battling wildfire flames throughout CA. Inmate firefighters serve a vital role, clearing thick brush down to bare soil to stop the fire’s spread.”

The tweet drew some surprise and protest. (The first response as of Thursday morning was, “Wait. What?”)

But California’s use of prison labor to fight wildfires is far from new. As Annika Neklason reported for the Atlantic, the program goes back to World War II:

Inmates have been fighting California’s wildfires since the 1940s, when the state first called up prisoners to replace men assisting the war effort. More than 3,700 men and women—and even some juvenile offenders—now voluntarily serve on the force. Collectively, they make up roughly a third of the state’s wildfire-fighting personnel, and work an average of 10 million hours each year responding to fires and other emergencies and handling community-service projects like park maintenance, reforestation, and fire and flood protection.

Inmates do get paid for the dangerous and potentially deadly work — but the pay is paltry, at $1 an hour plus $2 a day, and the hours are long, with the possibility of 72-hour shifts. Meanwhile, the inmate firefighting program reportedly saves the state $90 million to $100 million a year, according to California officials.

Some of the inmates say they appreciate the opportunity because they get better treatment and a sense of doing something good.

“It’s not just the [prison] walls you get rid of,” Michael Dignan, an inmate at the time, told KQED in 2014. “You learn a lot about yourself. You learn that there is stuff you can put yourself through that you never thought you would have been able to do.”

In California, the inmate firefighting work is supposed to be voluntary. It’s also an opportunity that inmates must earn, Neklason reported: “It comprises only inmates who earn a minimum-custody status through good behavior behind bars and excludes arsonists, kidnappers, sex offenders, gang affiliates, and those serving life sentences. To join the squad, inmates must meet high physical standards and complete a demanding course of training.”

Given that prison is a highly coercive environment in the first place, critics have questioned just how voluntary the work is.

As California’s prison population has fallen over the past few years, the state has struggled to refill its prison-fueled firefighting ranks, leading to a 13 percent drop in the number of inmate firefighters since 2008, even as the state’s fires have gotten worse in recent years.

California’s firefighting program, though, is only one part of the much broader use of prison labor across the US — some of which is not voluntary. The practice is explicitly allowed after the abolishment of slavery through the 13th Amendment of the US Constitution, which banned slavery and involuntary servitude “except as a punishment for crime whereof the party shall have been duly convicted.”

Prison labor has drawn a lot of criticism over the years. Several of the responses to CDCR on Twitter criticized the practice and questioned the agency’s use of “youth offenders” to fight fires. Arthur Rizer, who oversees criminal justice policy at the conservative R Street Institute, told the Washington Examiner that the treatment of inmate firefighters — many of whom aren’t even allowed to become firefighters once they leave prison due to their felony records — is comparable to “slave labor.”

California’s inmate firefighters have been caught in a broader debate about prison labor

This is not the first time that prison labor has become a national controversy, with the issue previously drawing attention during widespread prison strikes in 2016.

Hundreds of thousands of inmates across the US have daily jobs — not just firefighting, but also more typical jobs like kitchen work, cleaning, and GED tutoring. Sometimes the jobs will take inmates outside of prison, although more frequently they merely mimic real-world jobs or involve menial chores that need to be done around the prison. The average pay in state prisons is 20 cents an hour, according to the Marshall Project.

During the 2016 prison strikes, protesters characterized the practice as modern slavery. With black people disproportionately likely to be incarcerated, there are racial disparities in this often forced, low-paid labor. (It of course didn’t help that the Virginia Supreme Court said that prisoners are “slaves of the state” in 1871, six years after slavery and involuntary servitude were abolished by the 13th Amendment except as punishment for a crime.)

“Ultimately, the demand is abolishing prisons,” Azzurra Crispino, who helped organize the prison strikes, told me at the time. From inmates’ view, “the reason prisons exist is not to keep anyone safe — but because money gets made from prisons. So they’re saying, look, if the reason you have us locked up is because we make you a ton of money, then if we strike and you give us minimum wage, we won’t make you a ton of money anymore. And that will ultimately lead to reform for decarceration and prison abolition.”

Prison officials and other advocates argue, however, that prison labor can help inmates gain much-needed real-world working experience. Some research has backed this up: A study of federal prisoners found inmates who took part in UNICOR, the federal prison program, were 24 percent less likely to reoffend and 14 percent more likely to be employed a year after their release. And a study of a Florida program found significant increases in employment, but no changes in inmates’ likelihood to reoffend.

These studies aren’t definitive proof since they have serious selection bias issues. It’s difficult to know whether the inmates participating in prison labor programs are those who are already less likely to reoffend and more likely to get and keep a job after prison — since they’re able and, in some cases, volunteering to work while they’re incarcerated. Some studies try to control for this, but it can never be fully ruled out.

There’s another benefit to the work: It gives people something to do. “A lot of inmates have told me, ‘Look, jobs make the time go faster, and we want to be productive,’” Crispino said. “One of the things that’s frustrating about being in prison and especially solitary confinement is the forced idleness.” (To that end, she pointed out, strikes can actually make time in prison more dreadful, but inmates still said the protests are needed to voice discontent about what they see as abuses.)

But even if prison labor gives inmates something to do and improves their chances of reoffending and sustaining employment, there are still moral and ethical questions behind the practice as it’s done today. So the benefits may not justify paying prisoners pennies or nothing at all, but rather make a case for increasing the spending on these programs so everyone can participate and get at least minimum wage for their work.

Prison officials say they couldn’t afford to pay inmates more. They also argue that there are other costs that have to be considered that make this labor particularly expensive, such as the chance of lockdowns and costs of security — meaning, they say, that prison labor will never be able to be treated like a regular job in the free world.

For many inmates, this setup doesn’t feel like a fair deal. Another round of protests and strikes is planned for later this year, starting on August 21.