Everything changed with the French invasion in 1803 and the establishment, formally in 1805, of the Confederation of the Rhine, sponsored by France. Representing the Osnabrück regional administration, von Bar became a member of the standing deputation of the Kingdom of Westphalia, which in 1807 travelled to Fontainbleu and Paris in order to provide advice on a constitution for the puppet kingdom. A year later he was appointed president of the Court of First Instance in Osnabrück. He was also the special liquidator in respect of the national debt of the former Prince-Bishopric of Osnabrück. Between 1808 and 1811 he was a member of the electoral college for the short-lived department. Along with that, he was a member of the (almost equally short-lived) of the Kingdom of Westphalia.