A top U.S. Justice Department lawyer apologized to a federal judge on Monday for allowing his bar license to lapse as his name appeared on filings in a case challenging the Trump administration's move to subvert state regulations for vehicle emissions.

In a letter, Assistant Attorney General Jeffrey B. Clark said he discovered Dec. 9 that his license to practice law in Washington had been placed on "inactive status" in early October "for inadvertent non-payment of that year's dues."

Clark, the Senate-confirmed head of the Justice Department's environment and natural resources division, said he promptly addressed his lapsed bar license, paying the necessary dues along with a $280 penalty.

His letter to the court marked a rare court filing from a senior Justice Department leader. Clark, formerly a partner at Kirkland & Ellis in Washington, told the court he "also reported the dues issue to Justice Department authorities." The Justice Department's rules require lawyers to "immediately self-report to [Office of Professional Responsibility] any lapse in active bar membership during department employment." The professional responsibility office, widely known as at OPR, oversees DOJ attorney conduct matters.

"Upon further consultation with the relevant department office, I determined to bring the matter to the court's attention and I followed its advice on the form of this letter: Specifically, if because my name appeared on a filing I implicitly represented that my D.C. Bar license was active and was authorized to represent the United States at that time (Department attorneys must maintain an active state-bar license), I wish to correct any such implicit representation and extend my sincere apology," Clark wrote. "I was not aware of the lapse due to nonpayment of dues and did not intend to mislead the court."

Clark did not indicate how he learned his bar license had lapsed, and he was not immediately reached for comment Monday. Kirkland & Ellis "handled paying" his bar dues from 2006 until 2018, he wrote.

"The D.C. Bar did not have my correct address and I received no mail forwarded to me from my prior private law firm," Clark told U.S. District Judge Ketanji Brown Jackson of the District of Columbia. Clark further stated that Kirkland & Ellis moved to a new address in 2019. D.C. bar rules say lawyers need to update their address within 30 days of any change.

Clark's name appeared on filings the Justice Department made between October and early December in defense of the Trump administration's so-called "preemption regulation," a proposed nationwide fuel economy and emission standard for automobiles and light-duty trucks. The California Attorney General's Office, joined by more than 20 states and the District of Columbia, sued in November to block the regulation, arguing that it threatened to undercut more stringent state regulations designed to protect public health.

The California Attorney General's Office was not immediately reached for comment on Clark's letter.

Recent annual OPR reports revealed instances where DOJ lawyers self-reported lapses in their bar license. In one instance, the unidentified lawyer was newly licensed "and he received no written or electronic notice from the state bar regarding the annual registration fee." OPR stated in a report: "In addition, immediately upon learning of his suspension, he paid the annual registration fee, and he was reinstated. OPR concluded that further investigation was not likely to result in a finding of professional misconduct."

In another case, OPR reported: "Given the circumstances and the limited time period of the suspension, and because the DOJ attorney's bar license had not previously been suspended, QPR concluded that further investigation was unlikely to result in a finding of professional misconduct. Accordingly, QPR closed its inquiry in the matter."

Kirkland & Ellis Photo: Diego M. Radzinschi/ALM

Clark had been at Kirkland & Ellis—formerly the home to many Trump-era DOJ leaders, including U.S. Attorney General William Barr—from 2005 until his October 2018 confirmation as the assistant attorney in charge of the Justice Department's environmental division.

His clients at Kirkland & Ellis included General Motors, Mitsubishi Motors Corp., Volkswagen Group of America and Hitachi Ltd. Earlier, Clark was an associate at Kirkland from 1996 to 2001. His financial disclosure showed $963,000 in income from Kirkland in 2016 and 2017.

Clark's confirmation to lead the DOJ's environmental team marked a return to the division. He served in the division from 2001 to 2005 as a deputy assistant attorney general under the leadership of then-Attorney General John Ashcroft.

>> Read Clark's letter to the court Monday: