Carter signed FISA - however, the "inherent authority" was not his to give away, since it is a constitutional power of the executive - just as SCOTUS did not allow Congress to give the President a line-item veto without amending the Constitution.
In a way, this is a good debate - it is educating people about the nature of the relationship of powers between the various branches of government. And it is showing how the Dems politicize everything.
HOWEVER, the middle of wartime is NOT the time to be having such a debate!!!!
And he didn't give it away. He just submitted to congressional regulation. That's not the same thing at all.