"He's a lawyer and professor most famously known for helping give President George W. Bush the authority to torture suspects in the wake of the 9/11 attacks," begins Laura Hankin at Romper...
"John Yoo unleashed the 'unitary executive' theory that enabled Bush's torture program," adds Heather Digby Parton at Salon:
This essentially holds that during wartime a president can exercise virtually unlimited authority, which can be checked by Congress only by using the "power of the purse." Since the "war on terror" was a unique construct that could not possibly have a definitive end, that meant the president was to have nearly dictatorial power for the foreseeable future. Among other things, according to Yoo, the president could suspend the Posse Comitatus Act, which forbids the government to deploy the military for domestic police actions, and the Fourth Amendment, which prevents unreasonable searches and seizures, by holding that they don't apply to domestic military operations undertaken during a "war on terror."
Donald Trump's "enthusiastic endorsement of torture," as Parton puts it, mirrors that of members of the last Republican administration. "And they didn't just talk about it; they actually did it." While it is doubtful that the new President fully grasps Yoo's theory, he demonstrates the conviction that 'if the President does it, it's legal'.
Parton notes that "unfortunately, while Trump may not know or care about the legal precedents behind his actions, his lawyers surely do, and you can be sure they'll be citing Yoo's work on the unitary executive theory. No one could have predicted that Trump, of all people, would become president, but that's exactly why the cumbersome checks and balances were put in place to begin with."
The protestations that "Torture Professor" (who remains in the employ of the University of California, teaching 'ethics' to Constitutional Law students) makes against the way Trump exercises power do not begin to exonerate Yoo's contributions to operation of the State of Horror we suffer.