John Yoo isn't exactly a household name, but he should be. As a mid-level attorney in George W. Bush's Justice Department's Office of Legal Counsel, Yoo had "a hand in virtually every major legal decision involving the US response to the attacks of September 11, and at every point, so far as we know, his advice was virtually always the same -- the president can do whatever the president wants."
It was Yoo, for example, who advised in an August 2002 memorandum that El Presidente cannot constitutionally be barred from ordering torture in wartime.
It also appears likely that it was Yoo's legal reasoning that suggested that the president could simply ignore the FISA law in ordering massive eavesdropping of international communications by domestic sources.
Yoo is now back in private life as a law professor at UCLA-Berkeley, and he's written a book defending his legal interpretations of the power of the president. There's a book review of it here that is exhaustive in unpacking the dangerous reasoning that is unhinging our constitutional checks and balances.