For two decades, the federal government has pursued, prosecuted and sentenced cocaine offenders in a way that borders on insanity—targeting petty criminals over serious drug dealers—while fostering contempt, instead of respect, for the policies that have sent tens of thousands to jail. On Monday, the Supreme Court said enough was enough and empowered federal judges to reject sentencing guidelines rooted in hysteria and ignorance. The move has considerable support on the federal bench. It allows judges "who actually see the people and understand the local community," to better consider their communities' best interests, said Jack B. Weinstein, a federal district judge in New York.

The significance of the issue—and the enormity of the shift in expert opinion—was underscored a day later. The U.S. Sentencing Commission took the unprecedented step of announcing, unanimously, that nearly 20,000 federal inmates convicted of crack possession could apply for (relatively small) reductions in sentences. "In this business, you don't get too many good days … Now, two in a row," said Marc Mauer of the Sentencing Project, a Washington-based organization that tracks criminal-justice trends.

The court's two 7-2 decisions—authored by Ruth Bader Ginsburg and John Paul Stevens, respectively—contained no rousing rhetoric; they methodically built on the logic of two prior opinions. But Ginsburg's ruling catalogued, at length, criticisms of federal cocaine policy. "This may be the first sentencing decision since the mid 1980s that actually talks about justice, that seems to have some blood in it," said Graham Boyd, director of the ACLU's drug law reform project. Boyd compared the potential impact of Ginsburg's decision to the famous Brown v. Board of Education desegregation ruling. "When the Supreme Court says that something is wrong, the other institutions of government pay attention," said Boyd.

Ginsburg's carefully worded decision did not exactly say the Feds were wrong, but it explicitly gave federal judges permission to reach that conclusion on their own. The case revolved around a former Marine who had fought in Desert Storm and had no prior convictions and a good work record. Police found Derrick Kimbrough and a companion in a car with crack, powder cocaine and a gun. Kimbrough's guilty plea to four felonies should have sent him to prison for at least 19 years. The trial judge noted that had Kimbrough possessed powder cocaine in the same quantity as the combination of powder and crack, his potential prison time would have been more than halved. Judge Raymond Jackson split the difference, sentencing Kimbrough to 15 years. The appeals court said he was out of line; the Supreme Court ruled he was not.

On its face, the debate was over how much deference had to be paid to the guidelines; but it was also over whether those guidelines made sense. For embodied in them was the notion that a defendant caught with 50 grams of crack should face the same penalty as one with 5,000 grams of powder cocaine. Yet, crack is nothing more than powder cocaine and baking soda dissolved in water that is boiled away. And, as Ginsburg pointed out, they "have the same physiological and psychotropic effects." So why is possession treated so differently?

The answer lies in the Anti-Drug Abuse Act of 1986. In crafting the law, Congress concluded that someone dealing a small quantity of crack was the functional equivalent of someone dealing a large quantity of powder. Why conclude such a strange thing? Eric Sterling, then assistant counsel to the House Committee on the Judiciary, fingers an "expert consultant" named Jehru St. Valentine Brown. A narcotics detective when not advising Congress, Brown convinced legislators that "a trafficker in 20 grams of crack cocaine was trafficking at the same 'serious' level … as a trafficker in 1,000 grams of powder cocaine," said Sterling. Given such expert advice, it made sense to treat the drugs very differently—all the more so given the widespread conviction that crack was a superaddictive drug, spawning crack babies and rampant violence on a scale society had never before encountered. Fear took the place of science, leading the sentencing commission to adopt and build upon the 100-to-1 scheme embodied in the statute.