"In our democracy, the president is not supposed to dictate to the [attorney general] how to interpret the law," he wrote on Twitter. "This is a major breakdown in the rule of law.
"A president who fires an AG over this will think he can fire an AG over, say, a probe into whether his campaign coordinated [with] Russia."
The controversial orders Donald Trump has already issued
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He criticised the decision to replace Ms Yates with Dana Boente, the US Attorney for the Eastern District of Virginia, who was sworn in at a private ceremony and immediately. He is thought to be much less opposed to Mr Trump than Ms Yates, who had served under President Obama.
“I am honoured to serve President Trump in this role," Mr Boente said when he was appointed. "I will defend and enforce the laws of our country to ensure that our people and our nation are protected."
Mr Boente pondered whether the Trump administration had chosen Mr Boente precisely because he would follow orders.
"The next US [attorney] in line of succession was not Boente, but Zach Fardon," he wrote. "Did Trump go forum shopping for one who would follow orders?"
He said that people should oppose the move no matter how they feel about the Executive Order that banned refugees and people from seven Muslim-majority countries from entering the US.
"No matter what you think about the EO, the independence of DOJ is a principle that everything else in our democracy depends on," he wrote.
Lawyer and constitutional expert David Allen green echoed the comments, hailing Sally Yates as a hero.
"Far from "betraying" the @theJusticeDept, Sally Yates chose not to betray the Rule of Law," he wrote on Twitter, in reference to comments in the press release from Donald Trump. "A legal hero."
A follow-up post read: "Something is wrong when language of "treachery" and "betrayal" is used when sacking those upholding the US constitution and the Rule of Law".
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