Trump however, cannot likely revive torture with an executive order alone. In 2015, the Senate attached an amendment to the 2016 National Defense Authorization Act that banned torture by limiting interrogation techniques to those in the Army Field Manual, as Obama’s 2009 executive order had done. The Senate vote was overwhelming, 78-21, especially considering that Republicans controlled the chamber at the time. Senator John McCain, himself a torture survivor, issued a public statement saying that, “the President can sign whatever executive orders he likes. But the law is the law. We are not bringing back torture in the United States of America.”

Torture was also illegal when the Bush administration’s Office of Legal Counsel used what might be delicately called creative legal reasoning to interpret as lawful torture techniques the U.S. government wanted to adopt in its treatment of al-Qaeda suspects. Essentially, they argued that the president couldn’t be bound by laws restricting his ability to conduct military operations or defend the country.

But legal experts believe that this time, the legal language barring torture is close to ironclad, which means that Trump would most likely need an act of Congress to keep his campaign promises to do, in his words, “things that are unthinkable.”

Jack Goldsmith, a Harvard Law professor and former Bush Justice Department official, wrote on the legal blog Lawfare: “I am confident that the report that Trump gets from his top intelligence officials will advise him that a return to the bad old days is not legally available,” adding that “I am also confident that if President Trump ordered waterboarding, neither the CIA Director nor the Secretary of Defense would carry out the order.”

Similarly, Steve Vladeck, a professor of law at the University of Texas at Austin, wrote that while the order is “a really big deal,” there are now significant legal barriers set up by Congress and the courts to the resurrection of either the CIA’s “black site” network of secret torture chambers across the world, or the use of torture itself.

That doesn’t mean necessarily, that Trump couldn’t try to bring back torture unilaterally––but to do so he would have to rescind legal conclusions reached by the Justice Department’s Office of Legal Counsel at the end of the Bush administration and the beginning of the Obama administration. Not only that, but they would have to argue that the 2016 NDAA, enacted specifically to restrain the president’s authority to order people tortured, did not prevent the president from ordering people tortured.

“Formally they have the authority to do both of those things, but the optics of it would be so horrendous, even inside the government,” Vladeck told me. “There would surely be Justice Department lawyers who would resign in protest over the adoption of such a memo.”