The Supreme Court ruled 8-1 in favor of the defendant in Descamps v. United States, a case in which the defendant was charged with being a felon in possession of a firearm and faced a mandatory minimum 15-year jail sentence if the Court concluded he had been convicted of three prior "violent" felonies. Matthew Descamps had been convicted of burglary in California in 1978, but the question was whether this counted as a burglary for the purposes of the federal criminal law. The sentencing judge in the case reviewed the prior conviction and ruled it counted under the federal law, using what is known as a "modified categorical approach" of interpretation.
The Court rejected the way the judge made that determination. "In Plain English," SCOTUSblog writer and noted SCOTUS litigator Tom Goldstein concludes, "it is now harder for the government to use the facts of a prior conviction to enhance a federal criminal sentence." Elena Kagan wrote the decision for the court. Samuel Alito dissented. Anthony Kennedy and Clarence Thomas wrote separate concurrences.
Here's the decision: