Queen Isabella II's concordat (1851) : Text, Articles 1-4
To guard against the spectre of democracy, this concordat gave the Church a religious monopoly, and control of education and the press. It was abrogated by the Second Republic in 1931, but its first four articles were revived in Franco's 1941 Convention.
Though the democratic revolution of 1848 did not spread to Spain, its spectre strengthened the position of the Church. The throne wanted support from the pulpit to help foster the deference so necessary to counteract the heresies of liberty and equality. The price it paid was a new concordat in which it lost the traditional right to appoint clerics, the "royal patronage". In Articles 3 and 4 this royal preogative is quietly redefined as an obligation to support the bishops when requested: "Don't call us, we'll call you."
The concordat of 1851 made Catholicism the sole religion tolerated in Spain and granted the Church control of education and the press. (Objectionable books were no longer burnt, as they had been under the Inquisition: instead they were to be prevented from even being printed.) And what of the curious stipulation that the government help the bishops "oppose malicious attempts to pervert and corrupt the souls of the faithful"? A century later Cardinal Segura of Seville urged a return to Queen Isabella's concordat which used this clause to forbid the airing of Protestant ideas or Protestant worship for Spaniards. 
A few months later the concordat was given teeth through a draconian penal code, which inflicted imprisonment and exile for “any attempt to change the religion of Spain, for public worship in other faiths, for apostatising from [leaving] Catholicism, or for publishing doctrines in opposition to it”. The Spanish bishops even called for the revival of the Inquisition under their management. However, this would have been superfluous, since the new penal code proved quite sufficient for the repression of religious dissent. 
Spanish Concordat of 16 March 1851, Articles 1-4
The Apostolic Roman Catholic Church, to the exclusion of all other religions, will continue to be the only religion of Spain, always protected in the dominions of His Catholic Majesty and enjoying all rights and prerogatives according to God’s law and regulated by the sacred canon.
Accordingly, teaching in universities, colleges, seminaries, private and public schools of all types will conform in every respect to Catholic doctrine; and to this end no impediment of any kind will be placed on bishops and other prelates as they carry out their ministry to protect the purity of faith and customs and exercise their responsibility to educate the young, including those in public schools.
The clergy will not be impeded in any way as they carry out their functions, nor will any individual or pretext be allowed to disrupt the performance of their duties and responsibilities; on the contrary, the State will protect them and give them due respect and regard according to divine precepts and nothing will be allowed that might cause disrespect or contempt; His Majesty and the government will give its powerful patronage and support to the bishops whenever it is requested, principally when they oppose malicious attempts to pervert and corrupt the souls of the faithful or when they wish to prevent the publication, introduction or circulation of harmful books.
In all else pertaining to the right and the exercise of ecclesiastical authority and to the ministry of holy orders, the bishops and the clergy dependent on them will enjoy all the liberty established by the sacred canons.
Notes to introduction
1. "One Century's Saint . . .", Time, 25 August 1952. http://www.time.com/time/magazine/article/0,9171,816811,00.html
2. Henry Charles Lea, A History of the Inquisition of Spain, (Macmillan, 1906-07), Vol. 4, Book 9, Chapter 1, p. 469. http://libro.uca.edu/lea4/9lea1.htm
Translated by Barbara D. Wood
Articles 1-3 are online in Spanish at http://www.personal.us.es/alporu/legislacion/concordato_1851_educacion.htm