Re: Dear DOJ:
"Because the law doesn't yet recognise it as a legal form of tender?"
Does the US have to recognize the UK Pound to be able to trade with it? Not really. That's usually up to the banks and currency exchanges, who make the necessary arrangements. The government gets involved when its own currency gets handles, and that's usually sufficient, given transacting in the home country usually requires home currency.
Similarly, the US government takes the stance that as long as US dollars are used to exchange for Bitcoin, it has a say in the matter. That's why places like Coinbase register with the government to maintain legitimacy. Whether you consider Bitcoin as a currency, a commodity, or something else, as long as US dollars are involved, the US government, by default, is involved.