Washington (CNN) Chad Mizelle, a Trump administration official who is viewed as an ally of senior White House policy adviser and immigration hardliner Stephen Miller, has been tapped to be the Department of Homeland Security's top attorney.

The appointment, announced in an internal message obtained by CNN, comes after a year of turmoil in the top ranks of the department and amid major ongoing legal battles, including over the ban on trusted traveler programs for New York residents and a fight over asylum agreements to send migrants to Central America.

Mizelle, who was the acting chief of staff at the department, previously served at the Justice Department as counsel to the deputy attorney general and he completed a stint at the White House. He was appointed as acting general counsel by President Donald Trump , according to the department.

"I am confident that Chad will lead the Office of General Counsel with great honor and will continue to provide sound advice and counsel to Departmental leadership," the announcement from acting Homeland Security Secretary Chad Wolf says.

Mizelle has less than 10 years' experience as an attorney and will now run the DHS Office of the General Counsel, which oversees 2,500 attorneys and is ultimately responsible for all of the department's legal determinations.

Mizelle, a 2013 graduate of Cornell Law School, was an associate with a law firm where he represented New England Patriots quarterback Tom Brady in challenging his "Deflategate" suspension, according to a resume obtained through a Freedom of Information Act request by American Oversight, a non-partisan ethics watchdog that investigates what it says is misconduct in the Trump administration.

Mizelle also served as a law clerk at the DC circuit court and was an attorney volunteer for the Trump campaign in 2016, according to his resume.

"Mr. Mizelle's resume reflects a smart, capable attorney, but never in my wildest dreams would I have looked at it and seen the future general counsel of DHS in 2020," said American Oversight Executive Director Austin Evers, who pointed out that the department has a sprawling mission, from port security to immigration.

Evers said the qualities the Trump administration values the most are loyalty and an ability to push through its political agenda. "By putting a lawyer with little overall experience and no direct experience, it is reasonable to conclude that his qualifications are just those things -- loyalty to the President and the ability to carry out Stephen Miller's agenda."

Homeland Security spokeswoman Heather Swift pushed back on the criticism, saying it "sounds like political opponents or activists grasping for straws trying to criticize the administration as we add up continued policy successes."

"Chad is obviously experienced and anyone who has ever worked with him immediately recognizes his ability, patriotism, and focus on protecting the American people," she added.

Mizelle will be replacing a career official, who filled the void left after the previous Senate-confirmed general counsel, John Mitnick, was fired in September -- months after Miller wanted him out.

It is unclear if Mizelle will be nominated for the role, but the President has said he likes to have officials in acting capacities.

At the time Mitnick was ousted, there was a plan for Mizelle to fill the role, but the department needed someone to take over as chief of staff, a source said. Mizelle is viewed as "working Miller's agenda" at the department, the source added.

Miller, the architect at the core of the administration's immigration policies, had a hand in the purge within DHS last year, including the ousting of former Homeland Security Secretary Kirstjen Nielsen and a push to fire Mitnick, CNN previously reported

A former administration official said that Mizelle was first installed at DHS in early 2019 at Miller's direction. Another former official said that in one instance last year, Miller directed DHS staff to work with Mizelle on policy implementation when he was in the counsel's office.

"The revolving door at the top legal position at DHS should be of serious concern to members of Congress. After firing the Senate-confirmed General Counsel last fall, the President seems determined to bend the legal advice of this department to fit political objectives," CNN legal analyst and senior fellow at the Center for a New American Security Carrie Cordero said.

Wolf also announced Tuesday that John Gountanis, a former Immigration and Customs Enforcement attorney, will assume the duties of acting chief of staff.

Additionally, Tyler Q. Houlton, the former DHS press secretary , and Scott Erickson will serve as the department's deputy chiefs of staff. Houlton, the former press secretary under Nielsen, returned to the department when Wolf took over in the top spot.