PARIS—The U.K.'s Advertising Standards Authority Wednesday banned two Louis Vuitton print ads that it says could have misled consumers into thinking its products are handmade, when in fact the luxury brand also uses machines.

In the ads, artisans fold the leather of a wallet and hand-stitch the handle of a handbag. "What secret little gestures do our craftsmen discreetly pass on?" an ad asks. "Let's allow these mysteries to hang in the air. Time will provide the answers."

The...