The complete abdication of Congress

Glenn Greenwald weighs in on the Specter debacle:

The idea that the President's allies in Congress would enact legislation which expressly shields government officials, including the President, from criminal liability for past lawbreaking is so reprehensible that it is difficult to describe. To my knowledge, none of the other proposed bills -- including those from the most loyal Bush followers in the Senate -- contained this protective provision. And without knowing anywhere near as much as I would need to know in order to form a definitive opinion, the legality of this provision seems questionable at best. It's really the equivalent of a pardon, a power which the Constitutional preserves for the President. Can Congress act as a court and simply exonerate citizens from criminal conduct?