Six years prior to his effort sourced from an Alfred De Musset play, Eric Civanyan had transposed another play for the screen: "Tout Baigne" (1999) with underwhelming results. "Il Ne Faut Jurer...De Rien!" reproduces the same action from Civanyan with however slightly different results. It's a more appealing film than its predecessor but not necessarily a more palatable one. Maybe Civanyan is more in his element as a stage director as he had already directed his play on stage with some actors here.
The easy changes of space show that Civanyan succeeded in transposing his play to the screen, erasing thus problems of space. Splendid scenery, lush costumes are perfectly adapted to France in 1830 and confer to the film a strong appeal. The same goes for a clean cinematography. But although Civanyan remains faithful to Musset's spirit and set out his stalls for his work: under their frivolous, light appearances Valentin (Jean Dujardin) and Cécile (Mélanie Doutey) don't really believe in true love and the former loses himself in a life of debauchery, his film has major drawbacks that stop it from being a canonical work. First, in the type of comic employed. Between verbal comic lines, gags or situation comedy, the film has trouble to find its lasting comic tone and rhythm. Dialogs are old-fashioned: a modern re-writing wouldn't have hurt. See Jean Paul Rappeneau who rewrote with Jean Claude Carrière, "Cyrano De Bergerac" (1990). Besides, it would have been interesting to adapt the spirit of the play and its main themes with a contemporary eye. Instead, the director preferred to take refuge in a linear progression.
What about the cast? Jean Dujardin has the panache of Jean Paul Belmondo and beside him, Mélanie Doutey delivers a sparkling performance. Gérard Jugnot is good and it's the least we could expect from him but that's all. In counterpart, the actress acting Cécile's mother wasn't a judicious choice.
You can relax yourself with this little comedy but it is unlikely it stays for a long time in your mind.