WASHINGTON (AP) — The Supreme Court is making it tougher for federal prosecutors to seek longer prison terms for people convicted of repeated violent crimes.

The justices ruled 6-3 Thursday that lower courts are limited in how they can consider prior state crimes for purposes of increasing sentences under the federal Armed Career Criminal Act.

The court sided with Richard Mathis, who pleaded guilty to a federal weapons charge. He received a 15-year sentence — five more than he otherwise would have gotten — because of prior state convictions for burglary.

Mathis argued that Iowa burglary laws are broader than federal ones. But a federal appeals court said it could look beyond the elements of the state law to see whether Mathis' conduct would have violated federal burglary law.

The Supreme Court disagreed.