Until the short-lived Constitution of 1791 France's succession was ruled by custom, and these customs were enshrined in a system of laws which at various times were held, by those competent to adjudicate in such matters (primarily the Parliament of Paris composed of Magistrates and Peers), to be fixed and constant. The restoration of 1814 re-established the ancient Monarchy with all its pre-1789 powers and prerogatives, subject only to any limitations imposed by the Constitutional Charter of 1814 (article 74). The Charter did not attempt otherwise to regulate the succession to the Crown. It conferred on the members of the royal family (elsewhere defined as the children and grandchildren of the King) and on the Princes du Sang (Princes of the Blood), the right to a seat in the Chamber of Peers with precedence immediately after the President in order of their position in the succession, but these Princes could not take their seat without the prior permission of the King before each session, and could not vote until they were twenty-five years old.
The fundamental laws enshrined certain principles which bound the nation and the succession to the Crown for the first eight-hundred years of the Capetian Monarchy. During the interregnum of 1793-1814 these principles were applied to assure the titular succession of Louis XVIII rather than his niece, Marie-Therese, whom some French monarchists thought a more appealing focus for royalist loyalties. From 1815 they once again dictated the legal succession, and these selfsame principles were applied by French legitimists without dissent, until the death of Henri V (titular King), in 1883. These laws insured the peace of the Kingdom by allowing for there to be no doubt about the person of the heir to the throne, and thereby reducing the chances of a civil war over the succession. By preventing either the Sovereign, or any individual Prince, from alienating their own dynastic rights or those of other dynasts, these laws insured that personal preference or short-term interest could not divert the succession and thereby risk future challenges and dissent. The existence of fundamental laws which may not be overridden even by acts of the Sovereign registered in the Parliament is comparable to the supremacy of the Constitution of the United States, whose principles cannot be suborned by the acts of individual States or even Congress, and to parts of the modern French Republican Constitution which define the state as a Republic. In the USA, the individual states or Congress may pass laws which appear to have all the proper foundation which nonetheless may be struck down by the Supreme Court because if they conflict with the U.S. Constitution. In the same way a Monarch may issue properly registered decrees or letters patent that actually conflicted with the fundamental laws and were therefore void and ineffective. In France, there was no official body established to review these fundamental laws, but they were known and understood by all constitutional jurists
The French fundamental laws of succession may be identified as follows:
A. Succession to the Crown is limited to male princes descended from Hugh Capet.
B. Succession to the Crown must pass by primogeniture descent.
C. Neither the Sovereign, nor any other person or body, can divert the succession from the primogeniture male heir.
D. The House of France is one single House with reigning and non-reigning branches.
E. The nationality of a dynast does not affect his right
Go here to see the line of sucession from Hughes Capet to Louis XX