Allegations of Donald Trump’s criminality before taking office (tax evasion, fraud, money-laundering, sexual assault) and while he was President (obstruction of justice, criminal conspiracy) have brought into sharp focus the question whether a President is subject to criminal prosecution while in office. Brown thoroughly analyses the constitutional issues, including the separation of powers and the rule of law, implicated by presidential immunity from prosecution, as well as the constitutional and practical relationship between impeachment and criminal prosecution.