Complex sentence: Since 1959, Tibetans living in Tibet have been subject to the policies of the People's Republic of China and the Communist Party of China--under this regime, the Tibetan people's freedom of expression and political action are extremely limited.
Split into simpler sentences: Since 1959, Tibetans living in Tibet have been subject to the policies of the People's Republic of China and the Communist Party of China. Under this regime their freedom of expression and political action are extremely limited.