Duties
However, the nobles also had responsibilities. Nobles were required to honor, serve, and counsel their king. They were often required to render military service (for example, the impôt du sang or "blood tax").
The title of "noble" was not indelible: certain activities could cause dérogeance, loss of nobility. Most commercial and manual activities were strictly prohibited, although nobles could profit from their lands by operating mines and forges.
Read more about this topic: French Nobility