Congress overstepped its authority when it enacted a law allowing the federal government to hold sex offenders in custody indefinitely beyond the end of their prison terms, a federal appeals court ruled Thursday.

The law allowing civil commitment of "sexually dangerous" federal inmates intrudes on police powers that the Constitution reserves for states, many of which have their own similar statutes, a three-judge panel of the 4th U.S. Circuit Court of Appeals said.

Civil commitment power "is among the most severe wielded by any government," Judge Diana Gribbon Motz wrote. "The Framers, distrustful of such authority, reposed such broad powers in the states, limiting the national government to specific and enumerated powers."

In upholding a decision by U.S. District Judge W. Earl Britt of Raleigh, N.C., the 4th Circuit became the first federal appeals court to rule on an issue that has divided courts nationwide. A judge in Minnesota reached the same conclusion as Britt, while courts in Hawaii, Oklahoma and Massachusetts upheld the measure.

Thursday's ruling is binding only in the states included in the 4th Circuit: Virginia, North Carolina, South Carolina, West Virginia and Maryland.

U.S. Department of Justice spokesman Charles Miller said it was too early to comment on what steps the government might take next. The department could appeal the ruling to the U.S. Supreme Court or seek a rehearing before the full federal appeals court.