California Attorney General Xavier Becerra has chosen from the ranks of his office to find his next appellate practice leader.

Michael Mongan, a supervising deputy solicitor general in Becerra's office for the last five years, will assume the title of solicitor general next month. Mongan, who clerked for Justice David Souter of the U.S. Supreme Court, fills the role held by Edward DuMont, the former Wilmer Cutler Pickering Hale and Dorr partner who said in January he was leaving the attorney general's office after nearly six years in the post.

Mongan will take the reins of a 10-attorney office that plays a lead role in crafting California's legal strategy in response to Trump administration policies. The state has filed more than four dozen legal actions against the federal government since President Donald Trump took office in 2017.

“California was fortunate to have Ed DuMont as our chief appellate lawyer for the last five years, and we are equally fortunate to have someone like Mike, who cares so deeply about this state, to serve as California's next solicitor general,” Becerra said in a prepared statement. “Mike's commitment to appellate advocacy and his experience in leading some of the Department's most important appellate projects ensures that the Office of the Solicitor General continues in superb hands.”

During his time in the solicitor general's office, Mongan argued for the state in the U.S. Court of Appeals for the Ninth Circuit against Trump's rescission of the Obama-era immigration policy Deferred Action for Childhood Arrivals, better known as DACA. He also defended California's death penalty system in a 2015 case before the Ninth Circuit.

More recently, Mongan was part of the legal team that challenged the Trump administration's plan to place a citizenship question on the 2020 census.

In a statement issued by the attorney general's office, Mongan said he was “honored and humbled” by his appointment.

“I look forward to working with the team in the Office of the Solicitor General and our colleagues throughout the department to continue our tradition of excellence and success in our appellate practice,” he said.

A graduate of Stanford Law School, Mongan was deputy counsel to Vice President Joe Biden for the first two years of the Obama presidency. Mongan clerked for Souter during the 2007-2008 term. His co-clerks were Micah Smith, now a federal prosecutor, and professors Bert Huang, who teaches at Columbia Law School, and Leslie Kendrick, who teaches at the University of Virginia School of Law. Mongan earlier clerked for Judge Merrick Garland of the U.S. Court of Appeals for the D.C. Circuit.

merrick garland Judge Merrick Garland of the D.C. Circuit. Photo: Diego M. Radzinschi/ALM

In a 2016 interview with The Recorder about Garland's nomination to the U.S. Supreme Court, Mongan said his clerkship with the appellate judge “was the greatest legal education I could have obtained.”

“I like to think that when I'm writing a brief now there's a little Judge Garland telling me to dig a little deeper, to look around the corner at what I might be missing,” Mongan said.

DuMont has not said publicly why he is leaving the attorney general's office or where he is going next. He did not return a message sent to his office Monday.