It's clear from the article that the ring was found in Yorkshire, in the north of what is today England. In the fifth century (i.e. 1,600 years ago) that area was in transition from Roman to Romanized Britons' rule. The legions left around 410. If the ring was made in (what is now) France around that time it was most likely a Briton with connections to the Continent who brought it to Yorkshire. There was no "King of France" at that time.
It is good to know that British journalists can be as historically ignorant as their American counterparts. Well, nearly.