President Donald Trump dramatically fired Yates Monday night for "refusing to enforce a legal order designed to protect the citizens of the United States," the White House said
"(Yates) has betrayed the Department of Justice," the White House statement said.
The former prosecutors also said they could not have defended Trump's order had they been asked to do so.
"Struck by one stunning headline after another, we stopped to think: If we were called upon to defend the executive order, could we do it within the guidelines we learned and lived by as lawyers for the United States? We could not," the letter said.
"Acting Attorney General Yates
was right to refuse to do so. If her successor wishes to follow in the finest traditions of the Justice Department, he will reverse course and do the same," it added.
Yates had sent a letter to Justice Department lawyers saying her job was to ensure their position was "not only legally defensible, but is informed by our best view of what the law is after consideration of all the facts."
"In addition, I am responsible for ensuring that the positions we take in court remain consistent with this institution's solemn obligation to always seek justice and stand for what is right," she added.
Trump's executive order, signed Friday, bars citizens of seven Muslim-majority countries
from entering the United States for the next 90 days, suspends the admission of all refugees for 120 days and indefinitely suspends the Syrian refugee program. Yates' decision came amid a flood of protests against the executive order nationwide and after four federal judges ruled against Trump's order, staying its impact on people who were detained at US airports over the weekend.
The bipartisan group dates back to the 1970's and the signatories also include a number of former assistants to Rudy Giuliani, during his tenure as US attorney for the Southern District of New York.
The former New York City mayor was been a long-time Trump campaign adviser.
After Yates told Justice Department lawyers not to defend the travel ban, Trump promptly relieved her of her duties and installed Dana Boente, a US attorney, to serve in the acting capacity until Jeff Sessions, Trump's nominee for the post, is confirmed by the Senate.
Boente, nominated by President Barack Obama in 2015 for US attorney in Virginia, rescinded Yates' directive late Monday, instructing Justice Department lawyers to "defend the lawful orders of our President."
Yates had spent years defending Obama administration policies, championing changes to the criminal justice system and curtailing the federal government's use of private prisons.
In a written statement, Obama Attorney General Loretta Lynch lauded Yates, calling her leadership "courageous."
"(Yates) displayed the fierce intellect, unshakeable integrity, and deep commitment to the rule of law," Lynch said.
Eric Holder, Obama's first attorney general, also tweeted his support: "Sally Yates: person of integrity/attorney with great legal skill. Has served this nation with distinction. Her judgment should be trusted."