If you want to track them follow the money
Bitcoin is only semi anonymous. To make it really anonymous it needs money launderers. The question concerns how deep this rabbit hole goes. If Bitcoin has few legitimate purposes, then the cash to Bitcoin exchanges are money launderers too. Whether or not that is the case legally, those specifically offering anonymization services within this market seem legitimate targets for law enforcement, or if operating outside the jurisdiction of law, extra legal enforcement. E.G. see https://bitlaunder.com/anonymize-bitcoin
Biting the hand that feeds IT
