Complex sentence: They were cleared as safe for release from Guantánamo in 2005 or 2006, but US domestic law prohibited deporting them back to China, their country of citizenship, because the US government determined that China was likely to violate their human rights.
Split into simpler sentences: They were cleared as safe for release from Guantánamo in 2005 or 2006. But US domestic law prohibited deporting them back to China, their country of citizenship, because the US government determined that China was likely to violate their human rights.