Is Presidential Immunity in the Constitution?

Question: Could Congress, consistent with the Constitution, enact a statute making it a crime for any person to direct or participate in the use of American military force in the absence of a declaration of war by Congress against the target of that use of force?

Or how about being more direct in targeting the president: Could Congress make it a crime to issue a pardon to a person who has been convicted of conspiring to defraud the United States?

I think the answer to both these questions is no....