Federal investigation was into drug trafficking and illegal use of public funds, not whether Lance was doping (doping is not a criminal offence in itself, though defrauding companies by doing so might be). It could be argued that Lance commited perjury during previous trials when he actually used the USADA to 'prove' that he wasn't doping to get his bonus for winning the TdF 5 times.
Federal investigation was into drug trafficking and illegal use of public funds, not whether Lance was doping (doping is not a criminal offence in itself, though defrauding companies by doing so might be). It could be argued that Lance commited perjury during previous trials when he actually used the USADA to 'prove' that he wasn't doping to get his bonus for winning the TdF 5 times.