the thing that puzzles me is the why in all of this. The DEA can't fear people eating tons and tons of the stuff just to get high -- that's just not very likely. Ditto on somehow concentrating the trace amounts of THC, or they'd also ban poppies and the like. So why are they bothering to ban it?
Fresh-squeezed orange juice typically contains detectable quantities of ethanol (about 1/5 that of beer by volume). Perhaps the ATF should start regulating oranges to keep juvenile delinquents from chugging a gallon...
If you take this to extremes it gets stupid pretty quickly. Isopropyl alcohol (i.e. "rubbing alcohol") is one half of the binary to make Sarin nerve gas. I'll bet half the people on this list have "chemical weapon precursors" in their homes, a sure sign of criminal intent.