Self regulation of black markets on the dark web?

Here's an interesting story from the Guardian, about some dark-web black markets in the U.K. banning fentanyl, as too deadly and (hence) too likely to attract vigorous police attention:

Dark web dealers voluntarily ban deadly fentanyl
Suppliers, fearing police crackdown, decide opioid is too high-risk to trade

"Major dark web drug suppliers have started to voluntarily ban the synthetic opioid fentanyl because it is too dangerous, the National Crime Agency has said.

"They are “delisting” the high-strength painkiller, effectively classifying it alongside mass-casualty firearms and explosives as commodities that are considered too high-risk to trade.
...
"Vince O’Brien, one of the NCA’s leads on drugs, told the Observer that dark web marketplace operators appeared to have made a commercial decision, because selling a drug that could lead to fatalities was more likely to prompt attention from police.

"It is the first known instance of these types of operators moving to effectively ban a drug.
...
"O’Brien said that the NCA is working with US law enforcement agencies to prevent the UK from having a similar fentanyl epidemic, though the number of people dependent on opioids in the UK compared to America means it has a much smaller market."