I know nothing about American law, but why has the constant plea been for a pardon and not amnesty? It seems like in the former case one would need to be convi

I know nothing about American law, but why has the constant plea been for a pardon and not amnesty? It seems like in the former case one would need to be convicted of something before one could be pardoned. Snowden hasn't been convicted of anything yet... Although there is the caveat that amnesty at federal level would not provide immunity from prosecution by state courts, as far as I understand it. IANAL.