AIUI, Armstrong was given the all clear by a Federal Grand Jury, effectively saying he has no case to answer. Now you might have to ask an American if I am correct on this, but if I recall correctly, the US Federal Court takes a very dim view of lesser courts and agencies usurping its authority; they have a long history of walloping lower courts and agencies with a big stick. If this is correct, then even if Armstrong is found guilty by the USADA, he would be able to appeal to the US Supreme Court, who would, I have no doubt overturn any USADA decision if no other reason, to put them firmly in their place.