Yes. Any and all testimony he gave cannot be used against him. Any and all evidence gathered as a result of that testimony must be thrown out. And since he committed no actual crime in the US, there is no Constitutional jurisdiction for trial here. Only Congress can establish trial jurisdiction for crimes committed outside the US, and in this case Congress has done that for military tribunal only. The only recourse I see here is to try him for treason. It is the only Constitutional way for him to be convicted in a US civilian court.
Maybe the idea is to treat him as a Citizen of the World....
Then charge him with violating the standards of THAT...sets a precedent for others who would violate these new standards.....