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
Rainier III, Prince of Monaco was born at Prince's Palace in Monaco, the only son of Prince Pierre of Monaco, Duke of Valentinois and his wife, the Monegasque Hereditary Princess, Charlotte, Duchess of Valentinois. Rainier was the first native-born hereditary prince of Monaco since Honoré IV in 1758. Rainier's mother was the only child of Prince Louis II of Monaco and Marie Juliette Louvet; she was later legitimized through formal adoption and subsequently named heir presumptive to the throne of Monaco. Rainier's father was a half-French, half-Mexican who adopted his wife's surname, Grimaldi, upon marriage and was made a prince of Monaco by Prince Louis,