Russia’s intelligence service has refused to declassify the names of members of Stalin’s notorious three-judge panels that issued death sentences without trials, Russian media reported this week.

As many as 700,000 people were executed in Stalin’s “Great Terror” of 1937-38, according to conservative estimates. The Memorial human rights NGO keeps a database of some 3 million victims of Soviet repression.

At least two Moscow courts have sided with the Federal Security Service’s (FSB) refusal to grant gulag historian Sergei Prudovsky access to files containing the names of so-called NKVD Troika judges, Kommersant reported on Thursday. The NKVD was the predecessor of the Soviet KGB.

“[His] position could harm both the living relatives of officials who signed the protocols and the objective assessment of the 1937-1938 historical period,” senior FSB legal adviser Yelena Zimatkina reportedly told the court in response to Prudovsky calling the judges “butchers.”

Meanwhile, the head archivist in Novosibirsk region has barred researchers from accessing local NKVD files pending an examination for classified materials, the Znak.com news website reported on Wednesday.