Valuev Circular

The Valuev Circular (Russian: Валуевский циркуляр, Valuyevskiy tsirkulyar; Ukrainian: Валуєвський циркуляр, Valuievs’kyi tsyrkuliar) of 18 July 1863 was a secret decree (ukaz) of the Minister of Internal Affairs of the Russian Empire Pyotr Valuev (Valuyev) by which a large portion of the publications (religious, and literature used for school training) in the Ukrainian language was forbidden.

The Circular has put the reason for the growing number of textbooks in Ukrainian, and beginner-level books in Ukrainian with "the Poles' political interests" and the "separatist intentions of some of the Little Russians". The Circular also stated that "no separate Little Russian language ever existed, doesn't exist, and couldn't exist", and that the Little Russian is nothing more than the "General Russian" spoiled by Polish influence.

The Circular ordered the Censorship Committees to ban the publication of religious texts, educational texts, and beginner-level books in Ukrainian, but permitted publication of literature in that language.

Further restrictions were placed on the Ukrainian language by the Ems Ukaz in 1876, which completely prohibited the usage of the language in open print.

...
Wikipedia