and the executive branch to withhold information or documents from discovery in legal proceedings if such release would harm national security. Precedent for the privilege arose early in the 19th century when Thomas Jefferson refused to release military documents in the treason trial of Aaron Burr and again in Totten v. United States , when the Supreme Court dismissed a case brought by a former Union spy. However, the privilege was not formally recognized by the U.S. Supreme Court until United States v. Reynolds , where it was held to be a common law evidentiary privilege. Before the September 11 attacks, use of the privilege had been rare, but increasing in frequency. Since 2001, the government has asserted the privilege in more cases and at earlier stages of the litigation, thus in some instances causing dismissal of the suits before reaching the merits of the claims, as in the Ninth Circuit's ruling in Mohamed v. Jeppesen Dataplan, Inc. Critics of the privilege claim its use has become a tool for the government to cover up illegal or embarrassing government actions. The degree to which the president personally has absolute immunity from court cases is contested and has been the subject of several Supreme Court decisions. Nixon v. Fitzgerald (1982) dismissed a civil lawsuit against by-then former president Richard Nixon based on his official actions. Clinton v. Jones (1997) decided that a president has no immunity against civil suits for actions taken before becoming president, and ruled that a sexual harassment suit could proceed without delay, even against a sitting president. The 2019 Mueller report on Russian interference in the 2016 presidential election detailed evidence of possible obstruction of justice, but investigators declined to refer Donald Trump for prosecution based on a United States Department of Justice policy against indicting an incumbent president. The report noted that impeachment by Congress was available as a remedy. As of October 2019, a case was pending in the federal courts regarding access to personal tax returns in a criminal case brought against Donald Trump by the New York County District Attorney alleging violations of New York state law. Leadership roles Head of state As head of state, the president represents the United States government to its own people, and represents the nation to the rest of the world. For example, during a state visit by a foreign head of state, the president typically hosts