The first time Paul Fields was sentenced for a marijuana offense, he got probation. The second time, he got 100 days in jail. The third time, he got more than 15 years in prison.

That astonishing escalation was caused by a federal sentencing provision aimed at "career offenders," defined as people with two prior convictions for felonies involving drugs or violence who are convicted of a third such felony. Without that enhancement, which Congress seems to have mandated with scary predators in mind, Fields, who never hurt anyone and never even got to sell any of the marijuana from the 256 plants police found at his home in Jonesborough, Tennessee, would have faced a five-year sentence, the mandatory minimum for growing 100 or more plants.

A new report from the U.S. Sentencing Commission (USSC) recommends that Congress revise the career-offender provision to focus on violent criminals, which would avoid injustices like the one suffered by Fields. "The career offender directive fails to meaningfully distinguish among career offenders with different types of criminal records and has resulted in overly severe penalties for some offenders," the commission concludes. "The career offender directive should be amended to differentiate between career offenders with different types of criminal records, and is best focused on those offenders who have committed at least one 'crime of violence.'"

The USSC found that career offenders, who account for 11 percent of the federal prison population, "are sentenced to long terms of incarceration, receiving an average sentence of more than 12 years (147 months)." That's more than three times the average federal sentence imposed in fiscal year 2015. Most career offenders—74 percent in fiscal year 2014—are serving time for drug trafficking. Even federal prosecutors seem to be questioning the justice of these sentences. The commission notes that "career offenders are increasingly receiving sentences below the guideline range, often at the request of the government."

Focusing on violent criminals makes sense in terms of public safety. The USSC notes that "career offenders who have committed a violent instant offense or a violent prior offense generally have a more serious and extensive criminal history, recidivate at a higher rate than drug trafficking only career offenders, and are more likely to commit another violent offense in the future." The commission's recidivism study found that most career offenders who served time for drug trafficking (54 percent) were arrested again within eight years of being released, but they tended to commit new drug offenses rather than violent crimes.

"Under the current guideline, offenders can receive sentences of 15, 22, or even 30 years in federal prison, even if they had never spent a day behind bars previously," notes Mary Price, general counsel at Families Against Mandatory Minimums. "We could increase public safety and promote justice better by reserving the most serious sentences for the most serious offenders."

Focusing on violent criminals would also be consistent with the rhetoric of the politicians who supported the career-offender provision, which was enacted in 1984. It grew out of a 1982 amendment by Sen. Edward M. Kennedy (D-Mass.), a progressive icon who back then liked to attack the Reagan administration for being soft on crime. "The war on crime has been declared again and again," Kennedy told a conference of local prosecutors in July 1982, "and it has been lost over and over." He argued that the law needed to come down harder on "career criminals," since "it is likely that 50 percent of all violent crimes are committed by only 5 percent of all criminals."

President Ronald Reagan agreed. In a speech a few months later, he described "a class of repeat offenders and career criminals who think they have a right to victimize their fellow citizens with virtual impunity."

Kennedy emphasized violent crime, even saying (per the Associated Press's paraphrase) that "too much of the nation's scarce prison space is now filled by non-violent offenders." But the senator's amendment, which required judges to impose "the maximum or approximately the maximum penalty for the current offense" on "career criminals," included drug offenders. So did the version that Congress approved as part of the Comprehensive Crime Control Act of 1984, which established the USSC and required that its sentencing guidelines "specify a term of imprisonment at or near the maximum term" for career offenders.

That's how Paul Fields, a gentle and generous Deadhead with a new wife and an 8-month-old daughter, ended up with a 188-month sentence for growing marijuana. That is substantially longer than the average federal sentence for sexual abuse (134 months in fiscal year 2015), robbery (78 months), arson (62 months), or manslaughter (54 months). Despite the possibility that he would be sentenced as a career offender, Fields pleaded guilty to avoid charges against his wife. "I broke the law and deserve to be punished," hesays. But especially now that Fields' "crime" is treated as legitimate commercial activity in many states, his punishment seems grossly excessive.

Arrested in 2009, Fields went to prison in 2010. Now in his early 50s, he has served six and a half years and has not seen his 7-year-old daughter outside a prison visitors' room since she was a baby. "My relationship with my daughter is the most important thing in my life," he says. "Still, it's hard being separated…I keep a daily journal for her—every day I write a short little note to her, talking about my day, and what I know about hers. When a notebook is full, I mail it home and my wife saves them all together to give to her someday. I want her to always know how much I love and miss her, and that I think of her EVERY day."

Fields has asked President Obama to reunite him with his family by commuting his sentence. In a letter to Obama, Fields' wife, Pari, notes that he has taken many classes, held various work positions, and taught yoga in prison. "The recent legalization of cannabis in some states of the Union, together with his time served, strongly suggest that is time to bring him home so that he can return to being a hard-working, contributing member of society," she writes. "Most importantly, Paul needs to be home to resume his most important job: being a full-time father to our 7-year-old daughter, Corrina, who has no memory of her father living at home and keeps asking, 'When is Daddy coming home?'"

On the face of it, Fields seems like an excellent candidate for clemency. But Obama—who yesterday granted 214 commutations, raising his total so far to 562—is giving priority to prisoners who meet certain criteria, which include serving at least 10 years of a sentence that would be shorter under current law. Fields misses on both counts.

This article originally appeared at Forbes.com.

[The sentence that Fields would have faced without the "career offender" enhancement has been corrected.]