"Armigerous" describes someone who bears arms (a coat of arms). In French, you would describe such a person using a phrase like:
* "ayant droit à des armoiries" (literally: having the right to arms)
* "qui porte des armoiries" (literally: who bears arms)
* "blasonné" (this term means "blazoned" and refers to the act of describing a coat of arms)
You could also use more descriptive phrases like:
* "un membre de la noblesse" (a member of the nobility)
* "un descendant d'une famille noble" (a descendant of a noble family)
Ultimately, the best translation will depend on the context and the specific nuance you want to convey.