When the labour guilds of Brussels protested vigorously against the government taxes and tried to assert their ancient privileges, Prié caused the aged Frans Anneessens, syndic or chairman of one of these guilds, to be arrested and put to death (1719).
The citizens of Brussels have never forgotten to venerate the memory of their fellow-townsman as a martyr for public liberty. A square and a metro-station are named after Anneessens.
Prié also clashed with Claude Alexandre de Bonneval, the Austrian Master of the ordnance to the Low Countries and placed him in confinement. A court martial was again held upon de Bonneval, and he was condemned to death, but the Emperor commuted the sentence to one year's imprisonment and banishment. De Bonneval then offered his services to the Turkish government, was appointed to organize and command the Turkish artillery, eventually contributing to the Austrian defeat in the Austrian-Ottoman war.
De Prié stood down in the spring of 1725 to avoid dismissal. He returned to Vienna in disgrace and died a year later.