In a New York Times op-ed today, John Yoo wrote the following words: “even I have grave concerns about Mr. Trump’s uses of presidential power.”

That should get your attention, since Yoo, a fancy law professor at Berkeley, is best known for authoring much of the legal advice claiming the U.S. could legally engage in torture when he served in George W. Bush’s Justice Department.

In fact, Yoo believed this so fervently that in 2005 he said that a president can torture children if necessary, and there’s nothing that Congress or international law can do to stop him.

Yoo explained his perspective during a debate with Doug Cassel, then the director of Notre Dame Law School’s Center for Civil and Human Rights:

CASSEL: If the President deems that he’s got to torture somebody, including by crushing the testicles of the person’s child, there is no law that can stop him?
YOO: No treaty.
CASSEL: Also no law by Congress. That is what you wrote in the August 2002 memo.
YOO: I think it depends on why the President thinks he needs to do that.

You can listen to the audio of Yoo making that case here:

Yoo’s legal reasoning, as he (together with his superior Jay Bybee, who’s now a federal judge) advised the Bush White House, is that “the Department of Justice could not enforce Section 2340A [the federal probation against torture] against federal officials acting pursuant to the President’s constitutional authority to wage a military campaign.” In other words, the president can’t crush a 6-year-old boy’s testicles for fun, but if he thinks some child-testicle-crushing is needed to win the war, it’s totally constitutional.

The good news for Trump is that Yoo doesn’t express any concerns about Trump’s actions regarding foreign policy. Moreover, his qualms about Trump’s domestic actions are fairly mild. Yoo feels that Trump can’t pull us out of NAFTA, because that was enacted by Congress, and he can’t put a tariff on Mexican imports by himself. But he does think Trump can legally halt immigration from any countries he wants, although he believes Trump should be sure no one talks about it in public as a “Muslim ban.”

In the end, Yoo’s main quarrel with Trump is that Yoo thinks presidents can go totally hog-wild in foreign policy but should cooperate with Congress domestically — whereas Trump believes he can do whatever he wants overseas and at home. This troubles Yoo, because it could lead to Trump “dissipating his political capital and haphazardly wasting the executive’s powers” to really give foreigners the business.

Top photo: John Yoo in the law library at Chapman University School of Law in Orange, Calif. on Feb. 9, 2009.