WASHINGTON (BLOOMBERG) - The US Supreme Court said a Muslim prison inmate in Arkansas has a legal right to grow a half-inch beard, backing religious rights and rejecting the state's contention that facial hair would pose a security risk.

The justices unanimously ruled that the state's no-beard policy violated a 2000 federal law that requires prison officials to accommodate the religious practices of inmates when feasible. Arkansas argued unsuccessfully that beards would pose security issues by letting inmates conceal weapons or disguise their identity.

"The department has a compelling interest in staunching the flow of contraband into and within its facilities, but the argument that this interest would be seriously compromised by allowing an inmate to grow a 1/2-inch beard is hard to take seriously," Justice Samuel Alito wrote for the court.

Lawyers for the inmate, Gregory Holt, argued that his beard would be allowed in more than 40 states and the US Bureau of Prisons. The Obama administration backed Holt.

Holt is serving a life sentence in a maximum-security facility in Arkansas for stabbing his ex-girlfriend in the chest and neck.

The law at issue in the case, the 2000 Religious Land Use and Institutionalized Persons Act, is similar to a separate religious-freedom measure that applies in other contexts. The court in June used that law, the Religious Freedom Restoration Act, to rule that closely held companies can refuse to offer birth-control insurance coverage to their workers.