Jacques Necker, finance minister to King Louis XVI, had proposed that the King hold a Séance Royal (Royal Session) in an attempt to conciliate the divided Estates. The plan was agreed, however none of the three orders (see Estates of the Realm) were formally notified of the decision to hold a Royal Session. All debates were to be put on hold until the séance royal took place.
On the morning of June 20th the deputies were shocked to discover the doors to their chamber locked and guarded by soldiers. Immediately fearing the worst and anxious that a royal coup was imminent, the deputies congregated in a nearby indoor tennis court where they took a solemn collective oath "never to separate, and to meet wherever circumstances demand, until the constitution of the kingdom is established and affirmed on solid foundations".http://library.thinkquest.org/C006257/assets/events/tennis_court_oath_doc_4.htm The deputies pledged to continue to meet until a constitution had been written, despite the royal prohibition. 577 men signed the oath, with only one refusing. The oath was both a revolutionary act, and an assertion that political authority derived from the people and their representatives rather than from the monarch himself.