The Supreme Court issued its opinion in Johnson v. United States this morning, striking down the so-called “residual clause” of the Armed Career Criminal Act that enhances penalties for a “violent felony” as unconstitutionally vague. Writing for a 6-3 majority, Justice Scalia concluded that the portion of the statute applying to a crime that “involves conduct that presents a serious potential risk of physical injury to another” “denies fair notice to defendants and invites arbitrary enforcement by judges.”