Buying and selling bitcoin privately can constitute money laundering. There are many examples of people going to prison for buying bitcoin privately p2p. There have been many FBI stings that imprisoned people for showing up to a Starbucks to buy some Bitcoin. It's happened many times and that's a risk I'm not interested in.
Discussion
I think you're mixing things. If the user doesn't report cap gains, it's possible.
But the act of buying and selling crypto by itself via non-KYC paths is absolutely not a crime.
The user doesn't have any legal responsobility for verifying whether his counterpart is compliant with all the regulations or not.
buying and selling bitcoin p2p is absolutely a crime and many people have been imprisoned for it. Perhaps you are not aware of the history regarding this subject but I assure you that many have suffered from trying this path.
as a result all my bitcoin is purchased through US based KYC exchanges and every transaction I make is reported to the IRS. If you are doing anything differently then you are taking far more risk than I would.
Best of luck. And I mean that.