A bust of John Adams in Vizcaya testifying to his admiration for the system of Fueros in the Empire of Spain

(Fueros find an approximate parallel in the regional constitutions of England, such as custumals and local Anglo-Saxon oral laws sometimes codified as in St. Æthelberht's Law)

Two Medieval Spanish sayings evince the King's duty to these:
"en Aragón antes que rey, hubo ley"
"en Navarra hubo antes leyes que reyes"

The autonomy and localism of these regional constitutional rights, freedoms, and privileges were ironically violated by liberals.

The Olive Branch Petition is a glaring example of this traditional understanding where the American Founders appealed as loyal subjects and British citizens to the monarch against the encroachments and tyrannies of the Parliament until secession was inevitable.

The Ancien Régime recognized similar regional rights going back to codification of Salic Law, but the radicals of the new order post-French Revolution did not.

This liberal tendency of tyrannical centralist remained with the Bourbons & subsequently included their kin who then gained rule over the Spanish Crown. The "long train of abuses" included the church too, which is why the Mexican War of Independence prominently featured clergy.

Later in 1857 Mexico fell into a civil war known as the Guerra de Reforma for the liberal constitution denounced by Pope Pius IX, Archbishop José Lázaro stating that Catholics swearing allegiance to the Constitution would incur excommunication, & support resulting for Maximilian.

Etc.