alt Hacker NewsIt might be because there's a person in the photo, and France is very strict on photographing people.
https://commons.wikimedia.org/wiki/Commons:Country_specific_...
In terms of the formatting/brevity, Reuters was originally a wire service. They'd cover news in foreign locations and send it by telegraphic wire to local newspapers that would license the content.
Telegraphs charged by the word and didn't have letter case. Cryptic in-band signals like "NO USE FRANCE" are a relic of that time.
Since the link OP posted is to the B2B part of Reuters, I'm assuming they still haven't modernized this system.
It doesn't seem to be about photographing people, other pictures don't feature people and still have the "NO USE FRANCE" tag. It seems like all pictures by Chris Jung have the "NO USE FRANCE" tag.
My best guess is that Chris Jung has some kind of an exclusivity contract for publishing in France. Looking at his website, he publishes in "Paris Match", a French magazine, so it may be related.