The article examines the process of discussion and adoption of the provisional regulations of 23 March 1863 for people’s schools in the provinces of Vilna, Grodno, Kovno, Minsk, Vitebsk and Mogilev by the Western Committee in 1862–1864 and the role of the Chief Procurator of the Holy Synod A.P. Akhmatov in their adjustment. They allowed the use of “local languages” in teaching the Law of God to the Catholic Belarusians and Lithuanians as it had been suggested by the Trustee of the Vilna educational district, Prince A.P. Shirinskii-Shikhmatov and the governor-general of Vilna V.I. Nazimov, who did not give up the idea to combine “vernacular languages” with Russian in the elementary education even after the Polish revolt of 1863–1864. M.N. Muraviov, who succeeded V.I. Nazimov as the chief official of the Northwest region, sought to avoid radical approaches in the confessional sphere and preferred not to force the “withdrawal” of the Polish language from the teaching of the Catholic Law of God and introduction of the Russian (or Belarusian) language instead. However, the decisive factor that determined the practice of applying the temporary regulations of 23 March 1863 in 1863–1865 was a supplement to them, which was published in the journal of the Western Committee but was not inserted in the Complete Collection of the Laws of the Russian Empire. It was added at the initiative of A.P. Akhmatov and stipulated that the publication of any literature for the people in a “local language” relating to the Catholic religious education should be postponed pending discussion and final decision by the Holy Synod. Until 1865 when K.P. von Kaufmann was appointed the governor-general of Vilna, the unpublished supplement to the provisional rules was used by the Ministry of Public Instruction as the main argument against the introduction of the Russian language in the religious education of Catholic Belarusians in the Northwest region. In 1864 a similar initiative by the trustee of the Saint Petersburg educational district I.D. Delyanov in respect of Vitebsk and Mogilev provinces was rejected precisely on these grounds.