Switzerland's supreme court has forbidden the transfer of bank documents to Russia for its investigation into the defunct Yukos oil company, Swiss federal prosecutors said on Thursday.
The Lausanne-based Federal Tribunal said that, despite assurances from Russia, the nation's judicial standards fell short of the international norms required for Switzerland to comply with requests for legal assistance.
The decision is a blow to Moscow's efforts to obtain documents from Switzerland on companies and banks connected to Yukos, which was Russia's largest oil producer before being charged with tax evasion in 2004.
The company is now struggling to stay afloat after being ordered to pay billions of dollars in disputed back tax debts.
The ruling was a victory for Yukos founder Mikhail Khodorkovsky, who is serving an eight-year sentence in a Siberian prison colony after being convicted on tax evasion and fraud charges. Khodorkovsky brought the case to prevent the documents from being given to Russian prosecutors.
The court said in its legal explanation that, according to human rights observers, the proceedings in Russia were politically motivated, and therefore Switzerland's "cooperation must be refused.''
The 2003 arrest and subsequent trial of Khodorkovsky, a critic of the Kremlin, was widely seen as punishment for his support for Russia's opposition party.
"The political and discriminatory character of the procedure in Russia is underlined by the infringement of human rights and of the right to defense which have apparently been committed throughout the procedure," the court said.
Swiss prosecutors said they are trying to determine whether some US$200 million tied to Yukos can now be released. The money is all that remains from US$5 billion initially frozen in Swiss accounts, the largest amount ever blocked in Switzerland. Most of that money was previously released to account holders.