FinCEN Bitcoin Jan Clarification Release 1 by jasonmick
FinCEN Bitcoin Jan Clarification Release 2 by jasonmick
United States vs. Charles Shrem and Robert M. Faiella by timestaff
Sources: U.S. Department of Treasury - FinCEN, 
quote: You would have to simultaneously wipe the hard drives of millions of computers containing the block chain. For all practical purposes it's impossible.
quote: You would also have to have a giant EMP erase all offline hard drives and flash drives the world over while you are at it.