Bitcoin doesn't launder money, but does enable the barter economy to be more liquid and scalable. Barter is very difficult to tax, so there is the issue.
I have personally discussed this with a friend that is a federal reserve spokesman, so anyone that wants to argue otherwise should consider that first.
What's your daily ATM withdrawal limit? Familiar with the letters SAR? Mere suspicion of structuring requires a report. If you know any local people that work at a bank, ask he or she how many SARs are filed in the one branch per week, on average.
A major federal reserve branch maybe has $30 billion in cash on hand at any given time. The marginalization of the US cash market is almost complete after the past decade.
Lastly, consider the possiblity that those back scatter xray machines aren't about weapons.
It is not against the law. However, you are supposed to report barter transactions to the IRS. What percentage are actually reported is probably not all that high, but I have not seen any research on the topic.
I have personally discussed this with a friend that is a federal reserve spokesman, so anyone that wants to argue otherwise should consider that first.