Nigeria, Jan. 27 -- US President Donald Trump might leave an impression of violent novelty, at least for the leader of a nominal liberal democracy, soiling international relations with the gangster's touch. This sense of iconoclasm is misplaced. While his conduct regarding the abduction of Nicolas Maduro certainly dumps mightily on the precepts of international law, legal advisors in the US government have been constructing, with a mixture of deviousness and disingenuousness, the rationale for just that very thing over decades. Ditto the justifications for torture that will forever blight the administration of George W. Bush, and theories that elevate the presidential office above the scrutiny of Congressional and courts.

During his ten...