Bitcoin is a decentralised crypto currency Nd there is no such proper authentic regulating body over the bitcoin that could keep eye 👁 over all these bitcoin activities and most specifically the illegal ones like selling of drugs, explosives and money laundering and many more and being decentralised is also the one of the reason that its transactions fee is too high , once it will get legalised globally, though the transactions fee will obviously increase but I am sure that its illegal use can be stopped after its legalisation world wide.