Trump Says He Alone Can Do It. His Attorney General Nominee Usually Agrees.

“Generally, under the laws of war, absent treaty, there is nothing wrong with coercive interrogation, applying pain, discomfort and other things to make people talk,” he said, pausing, then adding, “as long as it doesn’t cross the line and involve the gratuitous barbarity that’s involved in torture.”

Later that year, Congress tightened laws against treating detainees in cruel or degrading ways, but Mr. Bush claimed he had constitutional power to do so anyway. In 2006, the Supreme Court ruled that the Geneva Conventions did require humane treatment of terrorism detainees, contrary to the Bush legal team theories that Mr. Barr had echoed.

Mr. Barr also repeatedly defended Mr. Bush’s decision to create the ill-fated system of military commissions instead of civilian courts to prosecute terrorism suspects. In fact, it was Mr. Barr who privately suggested to the Bush White House that it create a tribunals system, an idea he had considered as attorney general during the investigation of the 1988 bombing of Pan Am Flight 103. Two Libyan suspects were indicted in civilian court in 1991.

Mr. Barr has recounted a story about that case that may resonate with Democrats’ expressed concerns about whether he will maintain Justice Department independence against political interference by Mr. Trump. When prosecutors were preparing to indict the Pan Am 103 suspects, Mr. Bush cautiously asked his attorney general “would it be O.K.” to brief the National Security Council on the situation.

Taken aback at Mr. Bush’s hands-off attitude, Mr. Barr made clear that he saw the president as excessively deferential — and invoked the notion, popular among executive power maximalists, that the president, not the attorney general, is the prosecutor in chief.

Would it be O.K.? Well, I work for you; you’re the top law enforcement officer. Of course it’s O.K.,” Mr. Barr recalled marveling. “The attitude was, You have to be very careful with pending matters of justice.”