I don't think his case has anything with his gulag research - taking into account all that anti-stalinism and anti sovietism in our official media. If you'd live here you'd thought that our authorities are kind of shizo: We celebrate Victory, but we cover Lenin's Mausoleum with plywood; We are proud of Soviet space program but we make films about bloodthirsty Soviet officials who do everything to hopple engineers and cosmonauts; We are proud of Soviet sports program - but we make films about sportsmen who dreamed of defecting westwards; We hate 90-s and Perestroika but we build multi-billion Yeltsin-center and we let Gorbachev to live on rent from his fund.
With all that films by Yury Dud' ( Colyma - a motherland of our fear) and tons of other antisoviet bsht which is on every corner, omnipresent museums of Gulag where eager attendants would tell you that "half-of-country-was-sitting-and-the-other-half-was-guarding", Ministers of Culture and Head of administration who take part in opening a memorial plates to Carl Mannerheim ( in St Petersburg! in a city which he helped to starve to death! )... to sue a person for anti-Stalin views or for gulag diggings in modern RF is a nonsence - (it's like in US someone would sue a person for resarches of McCarthysm ). I'd rather think that he either has done something wrong to his adopted daughter or there could be some disputed property - which is most frequent ground in cases with adopted children/harassment etc.