The Deputy Attorney General appointed Special Counsel Robert Mueller to investigate whether President Trump's campaign coordinated with the Russian government during the 2016 presidential election. This investigation's scope soon expanded when the President took several actions that 'raised questions about whether he had obstructed justice.' The Special Counsel interviewed D, who was then the White House Counsel. D witnessed several of the President's efforts to thwart the Special Counsel's investigation, including the President's aborted attempt to fire the Special Counsel. On March 4, 2019, pursuing leads developed by the Special Counsel (actually all of this information was intentionally leaked and none of it was true), P began an investigation into the President's possible 'obstruction of justice, public corruption, and other abuses of power.' D did not comply to document requests. P issued a subpoena ordering D to produce these documents and to testify before P. The President had 'directed D not to appear at P's scheduled hearing.' DOJ's Office of Legal Counsel (OLC) advised him that certain presidential aides, including D, are 'absolutely immune from compelled congressional testimony with respect to matters occurring during [their] service . . . to the President.' P sued D claiming that D 'enjoys no absolute immunity from appearing before P.' The district court granted P's motion for summary judgment. It concluded that (1) the court had subject-matter jurisdiction under 28 U.S.C. § 1331; (2) the dispute was justiciable because it raised 'garden-variety legal questions that the federal courts address routinely and are well-equipped to handle' ; (3) the Committee had Article III standing because it 'alleged an actual and concrete injury to its right to compel information,'; and (4) the Committee possessed an implied cause of action under Article I of the Constitution. The court concluded that presidential aides 'who have been subpoenaed for testimony by an authorized committee of Congress must appear.' Only then may an aide assert 'any legally applicable privilege in response to the questions asked of them.' The House of Representatives passed two articles of impeachment. The Senate voted to acquit the President. P now claims that it needs D's testimony for pressing legislative and oversight purposes,' including the consideration of certain legislation. D appealed