Washington (CNN) A group of law enforcement advocates defended the Justice Department's new guidelines on drug prosecution in an op-ed posted Wednesday , writing that the Obama administration's policy of under-charging certain drug offenders had begun to leave a "devastating mark downstream on the safety of communities across the nation."

Since the inception of the Obama policy, the authors write, "correlative increases in drug abuse, overdose deaths and violent crime have had a devastating impact on every community, regardless of sex or demographics."

The piece, written by heads of professional organizations, including the National Association of Assistant US Attorneys and the National Sheriff's Association, and posted on the website of Fox News, toes the line of the new administration's Justice Department that blames the Obama policy for an increase in violent crime, and directly rebuts an essay published by former Deputy Attorney General Sally Yates last month in the Washington Post titled " Making America scared again won't make us safer ."

The "Smart on Crime" policy implemented by Yates and former Attorney General Eric Holder in 2013 included a directive to federal prosecutors to ignore mandatory minimum sentencing statutes for non-violent and low-level drug offenders. Under the initiative, the number of federal drug offenders not sentenced under mandatory minimum charges grew from 40% to 50% between fiscal years 2012 and 2014, a DOJ Office of the Inspector General's report released in June found.

Holder did not respond Thursday to a request for comment on the op-ed.

The sentencing practice was scuttled by Attorney General Jeff Sessions, who in May wrote a memo to federal prosecutors instructing them to "charge and pursue the most serious, readily provable offense."

In her op-ed, Yates questioned the trends employed by Sessions and proponents of the policy reversal.

"Not only are violent crime rates still at historic lows ... but there is also no evidence that the increase in violent crime some cities have experienced is the result of drug offenders not serving enough time in prison," Yates wrote. Sessions, who championed his change in a Washington Post op-ed of his own , was "stoking fear" with an argument that "just isn't supported by the facts," Yates wrote.

Since becoming the nation's top prosecutor, Sessions, formerly the US Attorney for the Southern District of Alabama, has used grim language to illustrate violent crime in a series of speeches across the country. In Memphis in May, Sessions described families in a local apartment complex that "live every day as hostages in their own homes, facing potentially deadly violence just to walk to the bus."

Memphis has in fact seen a recent uptick in murders: last year, the 650,000-person city hit a record of 228, surpassing a previous high set in 1993.

Early data for 2016 shows a year-to-year increase of 6.3% in violent crime across the country, with a smaller jump of 2.4% in the 30 largest cities, according to the academic Brennan Center for Justice.

But some criminal justice experts say backers of the narrative being pushed to support the new sentencing policy lack critical context.

The most complete national numbers for violent crime, from 2015, show that four cities -- Baltimore, Chicago, Washington and Milwaukee -- accounted for 20% of the overall increase, according to Ames Grawert, a counsel in the justice program at the Brennan Center.

"I think that the concentration point is not to be lost," Grawert said. "These might be cities that have decades of years in problems that they're dealing with."

Crime rates in large cities and nationally are also down significantly from high points in the 1990s, federal data shows.

"The Fox op-ed and those writers are broadly right in that as drug enforcement decreased in the last two years, crime rates also went up, but that's correlation. That's not causation in any sense of the word," Grawert said. "The problem is that the data is just too young to really be able to tell a story about what Smart on Crime did for crime rates."