Bloomberg reporter and former Donald Trump biographer Tim O'Brien thinks the one takeaway from the Supreme Court's argument over tariffs is that Chief Justice John Roberts may be trying to claw back the power the court handed to the executive branch.

Speaking to "The Weeknight," O'Brien said that he was keeping a keen eye on Roberts.

"It's interesting where Roberts sits because at different moments since Trump 1.0 and this term, he has weighed in in different ways around what a president can do unilaterally and what a president can do. And on some of the tax return rulings in the first term, he kept invoking, 'No one in America is above the rule of law, including the president. He has to release his tax returns.'"

But O'Brien said things changed in Trump 2.0, and Roberts wrote a "very thinly argued and damaging executive powers ruling and basically saying the president is above the law."

It appears now as if Roberts is trying to return to the matter and "say, well, maybe he's not that far above both the Constitution and the separation of powers and the law," O'Brien said.

"I think some of what you're seeing here is John Roberts working through his own view of some of this, trying to correct for past mistakes. I don't know that he can."