Administrative-Legal Analysis of the RF Constitutional Court Resolution No. 9-П, 24 March 2017The absence of its own legal solutions addressing the needs of public governance in Russian public law entails the application of civil law categories for the purposes of public law. Based on the example of unjustified enrichment, the article examines wither the transfer of civil law categories into public law domain is possible and in what circumstances the borrowed categories will be compatible with other public law doctrines. The establishing of a new public-law category - public-law claim for unjustified enrichment is being substantiated.