Software Exploits arent considered arms it is information that can be sold, the liability is on the person that does the unauthorized access, the person that steals data, the person that uses the data
Hacking syndicates distribute liability akin to any corporation
not about else and especially not for merely browsing or using or buying a legal good from a dark net market
as I wrote
Which is almost always the person finding the bug. Most services include language that limit your ability to find vulnerabilities in their systems as part of being allowed to access their service. If you find the vulnerability without ever accessing the service you might have an out, but that also means you have to sell the exploit with less ability to convince the buyer that it is something significant.
who would then argue they also sold it to security researchers, journalists and assumed everyone was or didnt discriminate or have any intent at all