Chief of Staff was a position within the Magical Congress of the United States of America, likely a rough equivalent of the No-Maj post of White House Chief of Staff. Thus, the Chief of Staff was likely responsible for aiding the President in managerial and advisory tasks, such as overseeing the President's support staff or managing the President's schedule.
In the 1920s, when No-Maj American society started enforcing Prohibition, some pointed out that not banning wizards from drinking alcohol made them rather conspicuous in cities full of sober No-Majs. President Picquery refused, saying that being a wizard in America was already hard enough, and famously telling her Chief of Staff that "The Gigglewater is non-negotiable".
Notes and references
|Magical Congress of the United States of America|