Currently, there is no French sovereign; three distinct traditions (the Legitimist, the Orleanist, and the Bonapartist) exist, each claiming different forms of title.
This title Rex Christianissimus, or Roi Très-chrétien owed its origins to the long, and distinctive, relationship between the Catholic Church and the Franks.
These philosophers believed that because he was rex christianissimus, the French king played a special role as protector of the Church.
It was recognized as independently sovereign and lying outside the Kingdom of France by Louis IV, an ally of Alan II, Duke of Brittany.
The duchy was inherited by his daughter, Anne, but King Charles VIII of France was determined to bring the territory under royal control.
During their marriage, the Charles VIII prohibited Anne from using the title Duchess of Brittany and imposed a royal governor from the House of Penthievre on the duchy.
Legally, however, the duchy remained separate from France proper; the two titles were linked only by the marriage of the king and queen, and in 1498 when Charles VIII died childless, the title Duke of Brittany remained with Anne, rather than passing to the heir of France, Louis XII.
When Anne died, Brittany passed to her daughter and heiress, Claude, rather than remaining with the king of France, her father.
Because Claude, like her mother, was sovereign Duchess, the title of 'Duke' did not remain with her husband, but instead passed to her son, Francis III of Brittany, who was also Dauphin of France.
He was also, by inheritance, a holder of other significant lands within France: Béarn, Donnezan and Andorra, which were, although a part of the feudal boundaries of France, were independent sovereignties; and, under crown jurisdiction, the duchies of Albret, Beaumont, Vendôme, and the counties of Foix, Armagnac, Comminges, Bigorre and Marle.
Henry, however, refused to follow this tradition: having no legitimate sons to pass his possessions onto, and forced to fight to secure his rule over France, he wanted to ensure that if he died without legitimate children, in the ensuing division of his inheritance, his sister Catherine would receive all of their parental inheritance (if he allowed his French lands to merge with the crown before dying without legitimate children, the merged lands would go as part of the crown to the next heir to the throne, his cousin Henri, Prince of Condé).
Accordingly, by letters patent of 13 April 1590, he declared that his personal estates would remain separate from the crown, and not subject to Salic law; in Letters of 21 December 1596, he further stated that "our ancient domain, in our kingdom of Navarre and sovereign land of Béarn and Donazan, low countries of Flanders, as well as our duchies, counties, viscounties, lands, lordships in this our kingdom, be and remained disunited, disjoint and separate of our house of France not to be in any way included or merged unless it is by us otherwise ordered, or unless God bestows on us the grace of having children we desire to provide thereto."
These acts were reversed in 1606–1607: Henry had a legitimate son, and the death of his sister without issue had nullified any need to share the Navarrese inheritance.
By an Edict of 1607, the original ruling of the Paris Parlement that lands within France were automatically merged in the Crown was upheld, and the king ceased to be Duke of Albret and Vendôme, Count of Foix, etc.
In October 1620, the merging of the Navarrese inheritance into France was furthered, when Louis XIII on 20 October had an Edict passed in Pau by the Sovereign Council of Navarre, to prevent "the misfortunes and inconveniences which would occur if, failing a male heir to our Royal House, said countries passed by inheritance to Foreign princes, thereby opening a door to enter into our Kingdom".
Unlike the British Act of Union, however, Navarre lost its independent judiciary, a fact the Navarrese resented for a long time afterwards.