By Euan McKirdy

CNN

(CNN) -- Sally Yates had been in the crossfire over her constitutional duty before her ouster Monday night as acting attorney general.

Video of Yates' 2015 confirmation hearing as deputy attorney general shows Sen. Jeff Sessions grilling her about her responsibility to then-President Barack Obama should he require her to execute "unlawful" views. Sessions is now Donald Trump's pick to lead the Justice Department.

"You have to watch out because people will be asking you to do things and you need to say no. You think the attorney general has the responsibility to say no to the President if he asks for something that's improper?" Sessions asks Yates.

"A lot of people have defended the Lynch nomination, for example by saying, 'Well, he appoints somebody who's going to execute his views, what's wrong with that?' " the GOP senator from Alabama asks, referring to Obama's 2014 nomination of Loretta Lynch as attorney general.

"But if the views the President wants to execute are unlawful, should the attorney general or the deputy attorney general say no?"

Yates replies: "Senator, I believe the attorney general or the deputy attorney general has an obligation to follow the law and the Constitution and to give their independent legal advice to the President."

An Obama appointee, Yates had been running the Justice Department while Sessions underwent confirmation as attorney general in the Senate.

She was fired Monday night after instructing Justice Department lawyers not to make legal arguments defending Trump's executive order on immigration and refugees.

"My responsibility is to ensure that the position of the Department of Justice is not only legally defensible, but is informed by our best view of what the law is after consideration of all the facts," Yates said in a letter to department lawyers.

The longtime Justice Department official paid the price for falling afoul of the Trump White House.

"(Yates) has betrayed the Department of Justice by refusing to enforce a legal order designed to protect the citizens of the United States," a White House statement said.

Yates' replacement, Dana Boente, the US attorney for the Eastern District of Virginia, was sworn in at 9 p.m. ET Monday, according to an administration official.

A few hours later, Boente issued a statement rescinding Yates' order, instructing Justice Department lawyers to "defend the lawful orders of our President."

The Senate Judiciary Committee is voting Tuesday on the nomination of Sessions as attorney general. It's expected to approve and advance him for a vote in the full Senate.