Could the United States bring back “enhanced interrogation techniques” — a fancy phrase for what Sen. John McCain (R-Ariz.) and others simply call “torture”?

After 9/11, the George W. Bush administration was widely criticized for using potentially deadly approaches to questioning prisoners. Since President Trump nominated Gina Haspel to run the CIA, human rights groups and some policymakers have worried that she might revive those programs – which apparently has led her to attempt to withdraw from consideration before her Wednesday hearings. The worry is because Haspel led the CIA “black site” in Thailand beginning in October 2002 and supervised the “enhanced” interrogation of detainees such as Abd al-Rahim al-Nashiri, the alleged mastermind of the 2000 USS Cole bombings.

But reviving torture is unlikely. Most of the loopholes that allowed the Bush administration to create the torture program have since been closed, as I’ll explore below. There are still some legal gray areas through which such techniques could reemerge — for example, how to interpret domestic and international legal proscriptions — but that’s not the only concern about Haspel’s nomination.

How did the torture program emerge?

After the 9/11 attacks, the Bush administration declared the country at war. And that enabled its lawyers to put forward a very broad vision of executive wartime power. In particular, John Yoo, a deputy with the Justice Department’s Office of Legal Counsel, argued that 9/11 constituted an act of war and therefore triggered the president’s powers as commander in chief.

In one well-known memo, Yoo offered the theory that a wartime president can overrule criminal laws, a breathtaking expansion of power. In this view, U.S. and international laws against torture did not apply to the president, as “Congress can no more interfere with the President’s conduct of the interrogation of enemy combatants than it can dictate strategic or tactical decisions on the battlefield.”

Haspel would not be the first Trump administration official who was involved in the Bush administration program.

Could Trump’s lawyers ever put forward this argument again? The outcry about Haspel’s nomination suggests that would be unlikely. But the first barrier against that argument would be the Office of Legal Counsel director, Steven A. Engel.

Like Haspel, Engel was involved with the Bush administration’s interrogation program. That came up during his confirmation hearings in May, when the Judiciary Committee asked him whether he had a role in drafting, reviewing or otherwise contributing to the OLC’s 2007 opinion on enhanced interrogation. That opinion declared legal six interrogation techniques: dietary manipulation, extended sleep deprivation, facial hold, the attention grasp, the abdominal slap and the facial slap.

Engel told the Judiciary Committee that he had indeed “reviewed and commented upon the draft July 2007 memo.” He refused to comment on whether the OLC correctly assessed that these techniques did not legally constitute torture, under the Geneva Conventions and the U.N. Convention Against Torture. As a result, McCain voted against his nomination — and announced that he would not vote “for any nominee who in any way has supported the use of enhanced interrogation.”

But if Trump wanted to bring the program back, his administration would face serious barriers.

After public revelations about Abu Ghraib, waterboarding, black sites and the like, all three branches of the U.S. government made clear that torture is unacceptable — and put obstacles in place to prevent its return. Let’s look at each of these.

First, in the judiciary branch, the U.S. Supreme Court affirmed in Hamdan v. Rumsfeld that the courts could decide when someone was wrongfully imprisoned in the military prison at Guantanamo Bay, which the Bush administration had argued put prisoners beyond the reach of civilian law and the U.S. Constitution. In Hamdan and related cases, including Rasul v. Bush and Hamdi v. Rumsfeld, the Court pushed back against the expansion of executive power outlined by Yoo and the Bush-era OLC.

Congress, meanwhile, pushed back against the torture program legislatively. In December 2014, the Senate Select Intelligence Committee released a 6,000-page review of CIA detention practices, detailing examples of misconduct by the CIA during its management of the detention program. In 2015, Congress passed an amendment to the 2016 National Defense Authorization Act (NDAA) that limited interrogation techniques to those contained in Army Field Manual 2-22.3, effectively banning torture — because that version of the Field Manual explicitly rejected practices from Abu Ghraib and Guantanamo, prohibiting such practices as waterboarding, forcing detainees to pose in a sexual manner, and placing hoods or sacks over the heads of detainees.

Opposing torture is a rare bipartisan issue in Congress. Few policymakers would want to risk political capital by restarting the program — although of course that could change if there were another attack on U.S. soil.

Finally, the executive branch also took action to ban any return of torture. On Jan. 22, 2009, President Barack Obama signed Executive Orders 13491 and 13492, which together sought to promote humane treatment of detainees. More explicitly, EO 13491’s section 3(c) revoked the OLC opinions that justified the torture program. Of course, Trump or a future president could reverse those orders — but not Congress’s torture ban.

But there’s more to the executive branch than the president. From 2003 to 2012, the CIA conducted accountability proceedings that assessed the actions of 30 individuals involved with the program when there were allegations of misconduct or noncompliance with the law, regulations or policy in the conduct of the program. Of those, 16 people were penalized for employing unauthorized interrogation techniques or being involved in the captivity of individuals who failed to meet the criteria for detention. One contractor was fired.

More broadly, the CIA internally examined its participation in torture — and rejected it, firmly. In fact, during the 2016 presidential election, former CIA director Michael Hayden said that if Trump wanted to return to waterboarding, “he better bring his own bucket.”

Personnel are policy — or, at least, policy messages.

In short, restarting the program would not be easy. Nevertheless, Haspel’s nomination may have worried policymakers that it signaled to the world that supervising torture doesn’t bar future promotion. As congressional leaders consider her nomination, they may wish to ask themselves whether that’s the message they want to send to the public, allies and the world.

Elizabeth Grimm Arsenault is an assistant professor of teaching in the security studies program at Georgetown University and the author of “How the Gloves Came Off: Lawyers, Policy Makers, and Norms in the Debate on Torture.” (Columbia University Press, 2017).