According to the Boston Globe's article :
"The office of Vice President Dick Cheney routinely reviews pieces of legislation before they reach the president's desk, searching for provisions that Cheney believes would infringe on presidential power,according to former White House and Justice Department officials.
"The officials said Cheney's legal adviser and chief of staff, David Addington , is the Bush administration's leading architect of the "signing statements" the president has appended to more than 750 laws.The statements assert the president's right to ignore the laws because they conflict with his interpretation of the Constitution.
U.S. News and World Reports describes Addington as "the most powerful man you've never heard of" in an article explaining who Addington is and what his significance is in our lives.
You can read up on the fellow in the Wikipedia entry under his name. It behooves us all to know who the invisible power brokers are and what they're up to.