(CNN) -- The European Court of Human Rights declined Monday to rule on the key points of a claim against Russia by relatives of victims of the 1940 Katyn massacre, but did rebuke Russia for refusing to hand over all of its files on the incident.
The court said it did not have the authority to rule on whether Russia had deprived the victims of their right to life because the World War II massacre happened before Russia joined the European Convention on Human Rights.
It also said the facts of the massacre were well established as a matter of historical record.
The World War II massacre, in which an estimated 20,000 Polish officers were murdered at point blank in the village of Katyn, tainted Russian-Polish relations.
For decades, the Soviet government blamed the killings on Nazi Germany.
In 1990, Russia finally admitted to what many in Poland had long suspected: The Soviet Union secretly murdered as many as 22,000 Polish soldiers and civilians in the early days of World War II in an attempt to pre-emptively suppress a Polish rebellion against communist rule.
That year, Russian prosecutors also launched a criminal case into the killings, but that case was closed in 2004. Since then, the country has handed over some investigation files to Polish officials.