[1] As his elder brother, Victor Amadeus, was heir to the Carignano princedom, the traditional occupations for a younger son of a princely house, an episcopal or military sinecure, beckoned him to the French court.

The marriage evoked a scandal, a lawsuit (conducted over many years by the renowned attorney, Lacretelle the Elder) and, eventually, an annulment ("for not having observed all the formalities prescribed by the civil and military laws of the kingdom") registered by the Parlement of Paris at the behest of Eugène's parents,[2] as well as the Kings of Sardinia and France, who objected to his elopement with the daughter of a family only ennobled since 1695, whose wealth derived from a prosperous apothecary ancestor.

[3] As the bridegroom persisted in his determination to wed Mlle de Boisgarin,[2] Louis XVI relented,[3] and King Victor Amadeus III issued a royal decree in September 1780 requiring consent of the head of the house for the marriage of princes of the blood, and morganatising marriages for brides of "inferior condition or status", whether wed with or without the royal assent.

[3] The only child born of this union, a son known as the Chevalier de Savoie, inherited Eugène's property when he died in his castle at Domart, Picardy, aged 31.

[3] Despite the Parisian mob's murder of his aunt, the Princesse de Lamballe, after the French Revolution he was made a page at the court of Napoleon I in 1812, became a colonel of the Hussars 2nd Regiment, and was promoted to lieutenant general during the Restoration.