The Cannes Film Festival was serious about those dress code rules—yes, even if you’re Halle Berry. As readers know, the film festival changed its dress code rules at the last minute, just as the stars began trailing into the French Riviera for the grand event.

“nudity is prohibited on the red carpet, as well as in any other area of the festival.”

The festival formally kicked off on Monday with the poster installation, then moved to the Hotel Martinez, where jury president Juliette Binoche and her fellow jurors dined on the eve of opening nigh...