China does not officially recognise dual nationality or the foreign citizenship of children born in China if one of the parents is a PRC national. If you have Chinese and another nationality you may, in theory, not be allowed to visit China on your foreign passport. In practice, Chinese authorities are not switched-on enough to know if you own two passports, and should accept you on a foreign passport. Dual-nationality citizens who enter China on a Chinese passport are subject to Chinese laws and are legally not allowed consular help. If over 16 years of age, carry your passport with you at all times as a form of ID.
Gambling is officially illegal in mainland China, as is distributing religious material.
China takes a particularly dim view of opium and all its derivatives; trafficking in more than 50g of heroin can lead to the death penalty. Foreign passport holders have been executed in China for drug offences. The Chinese criminal justice system does not ensure a fair trial and defendants are not presumed innocent until proven guilty. If arrested, most foreign citizens have the right to contact their embassy.