Defense Distributed sells a $1500 digital mill called the Ghost Gunner. Among other things, it can carve an aluminum AR-15 rifle body without a serial number. FedEx refuses to ship it.

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“This device is capable of manufacturing firearms, and potentially by private individuals,” FedEx spokesperson Scott Fiedler wrote in a statement. “We are uncertain at this time whether this device is a regulated commodity by local, state or federal governments. As such, to ensure we comply with the applicable law and regulations, FedEx declined to ship this device until we know more about how it will be regulated.”
But buying, selling, or using the Ghost Gunner isn’t illegal, nor is owning an AR-15 without a serial number, says Adam Winkler, a law professor at UCLA and the author of Gunfight: The Battle over the Right to Bear Arms in America. “This is not that problematic,” he says. “Federal law does not prohibit individuals from making their own firearms at home, and that includes AR-15s.”