In the Catholic Church an imprimatur is an official declaration by a Church authority that a book or other printed work may be published. Since, according to canon law, this permission must be preceded by a declaration (known as a nihil obstat) by a person charged with the duties of a censor that the work contains nothing damaging to faith or morals, the bishop's authorization of publication is implicitly a public declaration that nothing offensive to Catholic teaching on faith and morals has been found in it. The imprimatur is not an endorsement by the bishop of the contents of a book, not even of the religious opinions expressed in it, being merely a declaration about what is not in the book. In the published work, the imprimatur is sometimes accompanied by a declaration of the following tenor:
The nihil obstat and imprimatur are declarations that a book or pamphlet is free of doctrinal or moral error. No implication is contained therein that those who have granted the nihil obstat or imprimatur agree with the contents, opinions or statements expressed.
The person empowered to issue the imprimatur is the local ordinary of the author or of the place of publication. If he refuses to grant an imprimatur for a work that has received a favourable nihil obstat from the censor, he must inform the author of his reasons for doing so. This enables the author, if he wishes, to make changes so as to overcome the ordinary's difficulty.
If further examination shows that a work is not free of doctrinal or moral error, the imprimatur granted for its publication can be withdrawn. This happened three times in the 1980s, when the Holy See judged that complaints made to it about religion textbooks for schools were well founded and ordered the bishop to revoke his approval.
The imprimatur granted for a publication is not valid for later editions of the same work or for translations into another language. For these, new imprimaturs are required.
The permission of the local ordinary is required for the publication of prayer books, catechisms and other catechetical texts, and school textbooks on Scripture, theology, canon law, church history, or religious or moral subjects. It is recommended, but without obligation, that books on the last-mentioned subjects not intended to be used as school textbooks and all books dealing especially with religious or moral subjects be submitted to the local ordinary for judgement.
In 2010, Bishop Kevin C. Rhoades was the first bishop to grant an imprimatur to an iPhone application.