Monaco succession crisis of 1918 of this event, pursuant to the clauses of the treaty of 17 July 1918." The French government at the time was still the Vichy regime. Louis II died on 9 May 1949. The Principality of Monaco passed to his grandson, Rainier III. In the absence of an heir male, the ducal titles of Valentinois and Estouteville became extinct in French nobiliary law. Before Rainier III married Grace Kelly in April 1956, he notified the French government of his plans; the French ministry of foreign affairs replied with a message of official congratulations. Count Louis de Causans is suing the French
Honoré IV, Prince of Monaco V. Honoré IV, Prince of Monaco Honoré IV (17 May 1758 – 16 February 1819) was Prince of Monaco and Duke of Valentinois from 12 March 1795 to 16 February 1819. He was the son of Prince Honoré III by his wife, Maria Caterina Brignole, a Genoese noblewoman. After the fall of Napoleon I, he regained control of the principality thanks to a clause added by Charles Maurice de Talleyrand-Périgord at the Congress of Vienna stating that, " "the Prince of Monaco should return to his estates"", and passed on his titles to his eldest son, Honoré V, Prince of