They definitely don't, and it is no accident that they've maintained a state of uncertainty. After the B-cash hardfork created a potential taxable event, the IR

They definitely don't, and it is no accident that they've maintained a state of uncertainty. After the B-cash hardfork created a potential taxable event, the IRS refused to release any kind of guidance or warning for how they'd classify things - and there is a massive difference between short and long term capital gains tax. But they can't outright ban it, because development would continue outside the country. It would be a crippling self inflicted wound, because there will be a strong need in the near future for what bitcoin provides. In a world of autonomous software agents (short of self aware AI), meat space money won't work - due to clawbacks and human deceit. They'll eventually try a push for some kind of Fedcoin, but that will turn out the same way it did when the Canadians tried it. Until then they'll continue mounting their resistance at the fiat interface points.