I would venture to say that charges might conceivably be brought against any BO intruder, even if he did no damage whatsoever, on the basis of the Washington law. Regardless of the fact that the legal issues are complex, I think the ethical issues are very easily understood. Furthermore, I don't advocate it. My own brief exploits with BO, which I describe on my main BO page , are something I do not recommend to others, for a variety of reasons, but most of all for their own protection. BO's data packets are recognizable and traceable .
Countermeasures are in increasing use.
Regardless how innocent your actual intent, your ISP is justified in assuming you're up to no good if you're using the BO client. You'll probably lose your account, even if you've done nothing remotely illegal. Helping BO victims as I did is no longer a safe activity, well-motivated and even entirely ethical though it may be. As I see it, any use of the BO client should be very limited indeed. I remain willing to use it only on a known machine at a known address and with absolutely explicit permission.