A rarely enforced 1958 law—known as Decree Number 10—was invoked in May 1963 to prohibit the display of religious flags. This disallowed the flying of the Buddhist flag on Vesak, the birthday of Gautama Buddha. The application of the law caused indignation among Buddhists on the eve of the most important religious festival of the year, as a week earlier Catholics had been encouraged to display Vatican flags at a government-sponsored celebration for Diem's brother, Archbishop Ngô Đình Thục, the most senior Catholic cleric in the country.[18][19] However, Diệm proclaimed the flag embargo because he was annoyed with the commemoration for Thục.[20] On May 8, in Huế, a crowd of Buddhists protested against the ban on the Buddhist flag.