The lawyer, John A. Eisenberg, played a central role in dealing with the fallout at the White House from a July call between Mr. Trump and the Ukrainian president, in which Mr. Trump asked the Ukrainians to conduct investigations that could benefit him politically.
The committee subpoenaed Mr. Eisenberg to appear for questioning, but the White House informed Mr. Eisenberg’s lawyer on Sunday that Mr. Trump was directing him not to testify. The White House invoked absolute immunity, a sweeping and contested form of executive privilege that holds the president’s closest advisers are not obligated to cooperate with Congress.
“Under these circumstances, Mr. Eisenberg has no other option that is consistent with his legal and ethical obligations except to follow the direction of his client and employer, the president of the United States,” William A. Burck, a lawyer for Mr. Eisenberg, wrote to House leaders Monday morning. “Accordingly, Mr. Eisenberg will not be appearing for a deposition at this time.”
Mr. Eisenberg was not the only witness defying House investigators on Monday. Robert Blair, the national security adviser to the acting White House chief of staff Mick Mulvaney; Michael Ellis, Mr. Eisenberg’s deputy; and Brian McCormack, the former chief of staff to the energy secretary, Rick Perry, were all expected to skip scheduled depositions, despite receiving subpoenas.
The objections were not unexpected, but nonetheless showed the limits House Democrats face as their fact finding tries to edge closer into Mr. Trump’s inner circle. Additional witnesses scheduled to testify this week are likely to follow suit, either out of loyalty to Mr. Trump or because of complicated legal issues posed by their proximity to the president.
With their inquiry moving at a rapid pace, Democrats have made clear they do not intend to wait around for the courts to settle the legal issues raised by Mr. Eisenberg and others to secure their testimony. Investigators are trying to complete most private witness depositions this week, before beginning to make the case in public next week that Mr. Trump used the levers of his office to pressure Ukraine into investigating Democratic rivals for his own political gain.
“We are not going to delay our work,” Mr. Schiff said. “That would merely allow these witnesses and the White House to succeed in their goals, which are delay, deny and obstruct.”