The Senate Judiciary Committee passed a sentencing reform bill Thursday with the encouragement of its chair, Sen. Chuck Grassley (R-IA), but the divided vote belies strong opposition to the bill from some corners of the right, led in part by Attorney General Jeff Sessions.

Five of the Committee’s ten Republican senators, including Majority Whip John Cornyn (R-TX), refused to vote for Grassley’s bill, which will reduce sentences and remove mandatory minimums for certain drug offenders. Support for this opposition, however, also came from a former member of that body, long-time Alabama U.S. Senator Sessions.

Before his committee passed the bill on to the full Senate, Grassley (R-IA) became “incensed” Wednesday after Sessions sent him a letter warning that the sentence reductions in legislation Grassley is sponsoring would be a “grave error.”

Sessions sent a three-page letter on behalf of his Department of Justice (DOJ) to Grassley, his former colleague in the U.S. Senate, urging him not to pass S. 1917, a bill for which he is the chief sponsor.

“The legislation would reduce sentences for a highly dangerous cohort of criminals, including repeat dangerous drug traffickers and those who use firearms, and would apply retroactively to many dangerous felons, regardless of citizenship or immigration status,” Sessions wrote to Grassley. “In my opinion, if passed in its current form, this legislation would be a grave error.”

Grassley was apparently enraged that the attorney general would weigh in against his legislation at this early stage and shot back on Twitter:

Incensed by Sessions letter An attempt to undermine Grassley/Durbin/Lee BIPARTISAN criminal justice reforms This bill deserves thoughtful consideration b4 my cmte. AGs execute laws CONGRESS WRITES THEM! — ChuckGrassley (@ChuckGrassley) February 14, 2018

S. 1917 would reduce certain federal criminal penalties, mostly for drug offenses, by several means. The bill lowers some mandatory minimum drug sentences from 20 to 15 and ten to five years. It broadens existing “safety valve” provisions that limit application of these harsh mandatory minimum sentences and excludes so-called “drug mules” – those merely carrying drugs at the command of others – from the enhanced penalties that apply to higher-level traffickers. The bill, however, increases some sentences with new enhancements for the deadly drug Fentanyl and higher sentences for federal domestic violence charges.

Outside of sentences, S. 1917 includes general corrections reforms, including banning solitary confinement (“the hole”) for juvenile offenders in most circumstances. The bill also mandates several reviews of federal criminal statutes designed to address “overcriminalization,” particularly for regulatory offenses.

Sessions’s concerns lay primarily in the sentencing provisions, which he considered inappropriate while “[w]e are in the midst of the largest drug crisis in our nation’s history” and the violent crime rate is on the upswing. He warned off passing the bill, writing:

I would strongly urge the Senate to consider carefully the potential ramifications of this legislation in its current form. In recent years, convicted drug traffickers and other violent criminals have received significant sentencing breaks from the federal courts and the United States Sentencing Commission. Passing this legislation to further reduce sentences for drug traffickers in the midst of the worst drug crisis in our nation’s history would make it more difficult to achieve our goals and have potentially dire consequences. In addition, as you know, the Administration supports helping former inmates who have served lawfully imposed sentences and have demonstrated a commitment to a better life, and is working closely with Congress to achieve a responsible reform along these lines. Respectfully, this legislation runs counter to this serious Administration-wide effort.

Grassley then turned up the heat himself, telling Politico, “If he wanted to do this, he should have done what people suggested to him before: resign from attorney general and run for the Senate in Alabama again. We’d have a Republican senator.”

So far in his tenure at DOJ, Sessions has stood firmly against efforts to reduce drug sentences, including rescinding an Eric Holder era memo on the matter.

Grassley, by contrast, has joined sentencing “reform” efforts in recent years, sponsoring legislation to reduce penalties at the federal level in the last several congresses.