First of all, people take photos everyday of other people without consent. It is photography. General photographing is perfectly legal. Many artistic photographers, painters, drawers, sketch artists etc, like to capture a moment with a person unaware of their being drawn, painted or photographed because it is a more natural moment of human behaviour. If the photographer wished to use that photo for profit, then it would require the consent of the person in the photo to have it displayed publicly. People have to stop thinking of this as a twisted and voyeuristic tendency all of the time.

If you feel uncomfortable, then yes, he must respect it. If you have no issues with it and he is simply capturing a moment of natural human behaviour for personal enjoyment of a partner he cherishes, it could be seen as quite romantic. Just try to see all angles of the issue. It could be artistic expression, romantic attraction, a mild voyeuristic tendency, or something more concerning. Just don't automatically assume the worst.