WASHINGTON (AP) — The Supreme Court has struck down part of a federal law intended to keep people convicted of repeated violent crimes in prison longer.

The court on Friday ruled that a catchall phrase in the Armed Career Criminal Act, spelling out which crimes make defendants eligible for longer prison terms, is too vague.

The justices ruled in favor of defendant Samuel James Johnson, who pleaded guilty to federal weapons charges in 2012. Johnson was sentenced to 15 years in prison, 5 more than he otherwise would have gotten, because of his prior convictions.

That law lists some specific categories of previous crimes that can lead to a longer sentence. But it also says a violent felony includes crimes involving "conduct that presents a serious potential risk of physical injury to another."