The White House sent a blistering 8-page letter to House Democratic leaders on Tuesday informing them that the Trump administration will not participate in their impeachment inquiry into the president, blasting it as "constitutionally illegitimate."
Given that your inquiry lacks any legitimate constitutional foundation, any pretense of fairness, or even the most elementary due process protections, the Executive Branch cannot be expected to participate in it. Because participating in this inquiry under the current unconstitutional posture would inflict lasting institutional harm on the Executive Branch and lasting damage to the separation of powers, you have left the President no choice.