House Judiciary Committee Chair Jerrold Nadler (D-N.Y.) warned former White House Counsel Don McGahn on Monday night that if he ignores a congressional subpoena and refuses to testify before his panel on Tuesday, "the committee is prepared to use all enforcement mechanisms at its disposal."
Earlier Monday, White House Counsel Pat Cipollone notified Nadler that Trump had instructed McGahn to ignore the subpoena and skip the hearing. In a letter to McGahn, Nadler said "President Trump's order — which seeks to block a former official from informing a coequal branch of government about his own misconduct — is unprecedented," adding that this "does not excuse your obligation to appear before the committee."
Nadler listed several reasons why Trump cannot keep McGahn from testifying, including that "the president himself has already called your credibility into question." Nadler is referring to Trump tweeting earlier this month he "was NOT going to fire Bob Mueller," contradicting what McGahn told Special Counsel Robert Mueller. "In attacking your credibility and asking you to make public comments about these events, the president has not only further waived any possible privilege with regard to your testimony; he has also created substantial concerns about acts of witness intimidation and further obstruction of Congress' ongoing investigations," Nadler said.