The second defendant, Carlos R. Gould of Wichita Falls, Tex., pleaded guilty to a drug charge involving cocaine with a 10-year minimum sentence and the related gun charge with a 5-year minimum. The trial court gave him a little more than the minimum on the drug charge — 11 years and 5 months — and then added five years for the gun charge.

The question in the case was what Congress meant when it revised a 1968 federal gun control law in 1998 by, among other things, adding a new preface saying the five-year minimum for having or using guns while selling drugs applied “except to the extent that a greater minimum sentence is otherwise provided.”

Mr. Abbott argued that his 15-year-sentence for being a career criminal was such a greater minimum sentence and that it should cancel out the additional five years for the gun charge. Mr. Gould said the same thing about his 10-year sentence.

Justice Ruth Bader Ginsburg, writing for the court, said the defendants’ approach, which also relied on federal sentencing guidelines, might make sense as a matter of policy.

“We do not gainsay that Abbott and Gould project a rational, less harsh, mode of sentencing,” she wrote. “But we do not think it was the mode Congress ordered.”

It was implausible, Justice Ginsburg wrote, to think Congress had altered the law in 1998 in the direction of leniency. All Congress meant to say in 1998 was that defendants subject to a mandatory minimum sentence of more than five years for a particular crime — that of having or using a gun in connection with a drug crime — need only serve the longer sentence.

Congress did not mean to say, Justice Ginsburg went on, that any longer minimum sentence for unrelated crimes also canceled out the five-year gun sentence.

“We doubt that Congress meant a prefatory clause, added in a bill dubbed ‘an act to throttle criminal use of guns,’ to effect a departure so great from” the 1968 law’s purpose, she wrote. That purpose, she said, was “insistence that sentencing judges impose additional punishment.”

Indeed, she wrote, a broader reading of the disputed words could result in “sentencing anomalies,” including the possibility that “the worst offenders would often secure the shortest sentences.” ...