Professor Yoo argues that a congressional-executive agreement can substitute for a treaty, but he does not argue that an congressional-executive agreement IS a treaty. The two things are separate and distinct types of entities even if, in Professor Yoo's opinion, the former can in some circumstances substitute for the latter (setting aside, for the moment, the issue of how much weight one should give to the opinion of a man who, when he worked in Dubya's Office of Legal Counsel, argued that torture is not torture).