The European Court of Human Rights ruled that Poland violated the European Convention on Human Rights by allowing the establishment of a secret 'black site' at Stare Kiejkuty, which operated between 2002 and 2005, where the CIA illegally detained and tortured terrorist suspects. Two current Guantanamo detainees, Abu Zubaydah and Abd al-Rahim al-Nashiri, were transferred from Thailand to Poland by the CIA and tortured at the black site between 2002 and 2003.
This is the first case reviewed by the ECHR that involved accusations that a European country was complicit in the CIA rendition programme. More can be read here and here. The Court's press release can be read here. The judgments can be read here and here.