A constitutional crisis occurs when political parties willfully violate a constitution's law, as was demonstrated during the XYZ Affair, which took place in 1797 and 1798.
The XYZ Affair was a political and diplomatic episode in 1797 and 1798, early in the presidency of John Adams, involving a confrontation between the United States and Republican France that led to the Quasi-War. This was demonstrated by the so-called XYZ Affair, which involved the bribery of French officials by a contingent of American commissioners who were sent to preserve peace between France and the United States. In the course of government, the crisis results when one or more of the parties to a political dispute willfully chooses to violate a law of the constitution; or to flout an unwritten constitutional convention; or to dispute the correct, legal interpretation of the violated constitutional law or of the flouted political custom. 
