Hunter Biden’s lead criminal defense attorney on Tuesday asked a federal judge to remove him from the case because he could now be called as a witness in future proceedings.

Christopher Clark, a longtime Hunter Biden attorney, has vigorously defended the first son against the tax and gun charges, which could head to trial after a plea agreement crumbled last month.

In the court filing, Mr. Clark said that under the bar association’s witness-advocate rule, he is unable to continue his representation of Hunter Biden. That rule bars lawyers from representing a client if they are likely to be called as a witness in the case.

“Based on recent developments, it appears that the drafting of the plea agreement and diversion agreement will be contested and Mr. Clark is a percipient witness to those issues,” he and another lawyer wrote in the filing.

Mr. Clark wrote that his withdrawal will not harm Hunter Biden’s defense because other members of his legal team will continue to represent the first son.

Mr. Clark is stepping down only a few days after federal prosecutors said they’ve reached an impasse on a plea deal related to tax offenses and a division agreement to resolve a gun possession charge. They asked the judge to dismiss the case so they could bring charges against Hunter Biden in California.

The withdrawal also comes two days after Attorney General Merrick Garland granted special counsel status to Delaware U.S. Attorney David Weiss, expanding his authority to investigate Hunter Biden.

Last week, Mr. Clark said he was “confident” that Hunter Biden won’t face new criminal charges even after Mr. Weiss was named special counsel.

Another of Hunter Biden’s lawyers, Abbe Lowell, on Sunday said they believed the division deal was still “valid and binding.” Mr. Lowell blamed prosecutors for drafting the agreements that a federal judge in Delaware questioned because of an immunity agreement.

• Jeff Mordock can be reached at jmordock@washingtontimes.com.