But Democrats said that attempts by Kopperman and others to disobey summons will not delay their impeachment investigation, whether they decide to go to court to try to subpoena.
"We do not want to allow the White House to drag us into a long game of rope-doping in the courts," President of Intelligence Adam Adam Schiff said Monday after Cooper did not appear.
Schiff said he was confident the Chamber would eventually prevail in court, though he did not say whether the Chamber would follow this time – given that each trial would probably take weeks, if not months. to decide
"We expect the court to shorten this argument, but nevertheless, we are moving forward," Schiff said.
The chairmen of the three committees leading the House impeachment investigation dismissed Kuperman's case, threatening him with contempt if he did not appear. Democrats wrote in a letter Saturday that the suit was "an obvious and desperate tactic for the president to delay and impede Congress' legitimate constitutional functions and to conceal evidence of his conduct from the impeachment investigation."
Cooper responded by letter. Sunday claims that the summons is valid, and the president does not dispute Kuperman.
"If your clients' position on the substance of this matter is correct, it will prevail in court and Dr. Kuperman, I assure you again, will comply with the Court's ruling," Cooper wrote in a letter to the Court's Intelligence Committee .
Bolton, who was Kupperman's chief of the National Security Council, also hired Cooper as a lawyer.
Schiff, a California Democrat, told ABC on Sunday that he expects similar resistance from Bolton.
"We will hold public hearings and I think we will have them soon," Schiff said. "I do not want to set the exact time, because we are partly struggling with the White House's continued efforts to impede our investigation, to prevent witnesses from entering. I suppose they will fight us with John Bolton, for example."  While Democrats have so far successfully fought the Trump administration in the courts – a judge ruled Friday that the impeachment investigation is valid – trying to force Cooper or Bolton to testify through contempt or in the courts is a key problem for the Democrats: it will take weeks, if not months, to prevail.
Schiff and other Democrats said earlier that witnesses and agencies that refute summonses for documents and testimony obstruct Congress, which can be cited in impeachment articles, but Kuperman is the first witness to impeachment contempt for not showing up.
This week there are five additional witnesses who will appear behind closed doors for deposition, including Tim Morrison, an official on the National Security Council, who was quoted repeatedly in the testimony of US diplomat Bill Taylor. Three more volunteer-fighting officers were called in to appear next week.
This story was updated with additional updates on Monday.