On page 17 of the Forfeiture Complaint (PDF) it says
Federal agents obtained the warrants after tracing a number of Bitcoin transactions originating with AlphaBay to digital currency accounts, and ultimately bank accounts and other tangible assets, held by CAZES and his wife.
Oh, FFS. His computer was turned on and not encrypted or protected so of course LE had access to his bitcoin after they arrested him. There is no evidence that the blockchain had anything to do with his arrest. On the contrary, his numerous opsec failures leading to his arrest have been well documented - such as having the same hotmail address in his linkedin profile as the CMS configuration used for every welcome to alphabay message. Google it before you spread nonsense please.