I sometimes sell BTC in local market through the help of some facebook group. I never felt that I am in risk but for the first time, it seems like we are actually risking ourself a lot of by selling BTC to unknown. What if they get a trace of ourself and link us with such transactions? Would we be also get punished? For your info, we had to use our mobile number to continue dealing.
I believe you would be punished if you knew you were trading with criminals and all your activity info were being tracked by your authorities. At least that is what I saw on the cases on which middlemen and traders were punished with the criminals.
But on those cases there are a lot of investigations which run for several months or years, so the police can collect irrefutable evidences against the parts involved. If you are an innocent bitcoin buyer/seller there won't be any evidence to be collect, so you are safe.