[1][2][3][4][5] These levels are not hierarchical, meaning there is no supremacy or primacy of one over the other, but rather they are separately defined by their jurisdictional powers (Spanish: competencias).
Related to provinces, there is another territorial division of Spain into 431 judicial districts which are the constituencies for the election of provincial councils.
[13] It has been suggested that the territorial model is the most imprecise and deliberately ambiguous area of the Constitution due to unresolved controversy and political tensions when it was being negotiated.
[14][15] Although Spain is considered one of the most decentralised countries in Europe, its form is not defined in the Constitution and has been the subject of much debate.
[19] A more recent assessment is[24] Among political scientists and other foreign scholars, there seems to be a consensus that the Spanish model can be regarded as a federal system with certain peculiarities...The powers that belong exclusively to the state are defined in the Constitution[25] and those of the regional governments in their statutes of autonomy and can include housing, urban and regional planning, agriculture, transport, health, education, social welfare and culture.
[28] However one aspect of this asymmetry is a cause of friction, namely that the Basque Country and Navarra can raise their own taxes and negotiate a transfer to Madrid to pay for common services and hence, unlike the other regions, do not contribute to fiscal equalisation across Spain.
[29] Numerous powers are shared between national and regional governments such as the regulation of education, municipal supervision, social services and universities.
[38] Another writer says that provinces, as instruments of centralist thinking, are anomalous in a constitution that created a framework of autonomous communities.
In six (Asturias, Cantabria, La Rioja, Madrid, Murcia, and Navarre), provincial functions are assumed by the regional government because the boundaries are identical.
The use of territorial units or geographical boundaries for statistics, European policy development and funding, and for other geospatial purposes is distinct from the jurisdictional powers given to the three spheres of government.
Using a different numeration scheme the US Federal Information Processing Standards region codes defines the autonomous communities and cities as first-level subdivisions (19 in all) but only the 50 provinces as second-level.