An interesting article (in French), after a few web search.

Relevant point for our debate :

- first indications of censorship date back to Suvorov expedition in Italy

- censorship was instated by Alexandre Ier in 1807, again by fear of external influence on Russian society

- librarians and editors were responsible for unauthorised publications, incurring exile or expulsion (many were Germans).

- censorship had two standards, one for upper class readers, who could access uncensored version under individual grant. The other for commoners, where censorship of russian text was so heavy that "one could not imagine that social system other than the Russian one could exist on earth"

- not only French publications, but also germanic ones were supervised, which could affect the large german-born population of the Empire. Even the extremely conservative Prussian newspapers could be banned. English production, readable by very few people, were tolerated.

- in one extreme instance, censorship case was secretly tried by a committee of senior public officers, involving disappearance of the culprits, until relatives took him out of jail, without explanation.

Source : Véra Miltchina, « La censure sous Alexandre Ier vue par un diplomate français », colloque Les Premières Rencontres de l’Institut européen Est-Ouest, Lyon, ENS LSH, 2-4 décembre 2004, (see link)