The foundations of Basque home rule were badly shaken at the turn of the 19th century, followed by the short-lived but watershed Spanish nationalist Constitution of 1812 (Cádiz). The above districts restored their sovereign native institutions and laws still up to the end of the First Carlist War (1839–41), when a decree by Regent Maria Christina established the annexation to Spain (referred to as "Constitutional Spain", after the 1837 Spanish Constitution), still keeping a reduced, ambiguous self-government status ("fueros"). However, new senior officials in Navarre (a kingdom up to that point) signed a treaty apart from the rest of Basque historic districts, converting it into a regular Spanish province (1841), except for a small but relevant set of fiscal prerogatives.