If you're referring to the arrest of Green in the beginning, the authorities had built up a case that Green was a major player in the Silk Road and the package

If you're referring to the arrest of Green in the beginning, the authorities had built up a case that Green was a major player in the Silk Road and the package delivery was the final confirmation. You seem to be talking about entrapment, but entrapment is when law enforcement induces someone to commit a crime they would otherwise not have committed. Here they had evidence that Green routinely arranged and received drug shipments, and that this final shipment made by an undercover officer was part of that routine.