I don't understand what you're trying to get at here. You're slicing and dicing this thing to the n-th degree on a strained hypothetical.
It is the responsibility of the two parties to know the laws and conduct the transfer within the laws. If one or more of the parties does not, it is the responsibility of the state or federal government to enforce the law.
If you murder someone in the woods and are really good at hiding a body, then maybe you'll get away with it. You still broke a law, if there's evidence that can tie you back to the crime in question, it will be prosecuted.
[ETA: ha, guess I'm on the same wavelength as Len with the murder analogy]