Under Section 54(1) of the Police Force Ordinance (Chapter 232), it is lawful for a police officer to stop a person who is acting in a suspicious manner. The police officer may require that person to produce proof of identity (i.e. by showing a Hong Kong ID card or passport), and detain that person on the spot for a reasonable period to make enquiries into whether or not the person is suspected of having committed any offence at any time. What constitutes a "suspicious manner" is based only on the subjective assessment of the police officer. However, the police officer must, in fact, have a genuine suspicion.
Section 49 of the Public Order Ordinance (Chapter 245) permits a police officer to require any person to produce proof of his identity for inspection for the purpose of preventing, detecting or investigating any offence. A failure by that person to produce proof of identity under these circumstances constitutes an offence.
The police and immigration officers also have power under Section 17C(2) of the Immigration Ordinance (Chapter 115) to demand any resident in Hong Kong aged 15 or above to produce proof of his identity for inspection. A failure by that person to produce proof of identity as required without reasonable excuse constitutes an offence and is liable to a fine of $5,000.