Washington (CNN) Attorneys for Charles Kupperman, the former deputy national security adviser who hasn't testified about President Donald Trump and Ukraine after he tied up his House subpoena in court, are doing what they can to keep his lawsuit alive.

Kupperman's attorneys asked a federal court Wednesday to add House Sergeant-at-Arms Paul Irving as a defendant in Kupperman's case, saying how he fears receiving another subpoena if his case gets dismissed, and grasping onto the idea that the President can be sued because he isn't above the law.

The requests to the DC District Court come just days after a federal judge decided that former White House counsel Don McGahn had to testify, and that White House officials aren't immune from House subpoenas. McGahn's case is currently headed to an appeals court.

Kupperman's request to add Irving as a defendant is a way to potentially save his case. Kupperman's case appears to have major issues regarding whether he can sue members of the House, because House members say they cannot be sued under the Speech and Debate Clause of the Constitution.

"Even if the House Defendants are immune from suit, the Speech or Debate Clause does not here apply to the Sergeant-at-Arms," Kupperman's attorney, Charles Cooper, wrote on Wednesday. He notes the White House has no opinion on whether Irving should be added to the case, but the House might respond at a later time.

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