It is universally accepted among communities in which the rule of law prevails that no criminal offence can be retrospective. No one can be found guilty of a criminal offence passed into law after the event on which he was charged.
This is enshrined in article 15 of the International Covenant on Civil and Political Rights (ICCPR), which is incorporated as article 12 of section 8 of the Hong Kong Bill of Rights Ordinance (BORO), Cap 383. Under the Letters Patent, the present 'constitution' of Hong Kong, no law contravening the ICCPR is to be enacted. Under article 39 of the Basic Law, the ICCPR remains in force, and no law may make restrictions to the rights and freedoms of Hong Kong residents contravening the ICCPR.
It is therefore clear that any provisions for criminal offences in the Reunification Bill to be passed in the small hours of July 1, can have no retrospective effect. A person cannot be found guilty of something he did in the hours before the bill is passed, on the strength of the legal effect of that bill after it is made law.
It is said that nevertheless the Reunification Bill may have retrospective effect by operation of Hong Kong law. Section 20(2) of the Interpretation and General Clauses Ordinance says: 'An ordinance comes into operation (a) at the beginning of the day on which it is published.' A bill passed by Legco has to be assented to first by the Governor before it can be published in the Government Gazette. The preparation for publication will need some time. In the normal course of events, publication will not be on the same day.
Supposing the Reunification Bill is assented to by Chief Executive Tung Chee-hwa as soon as it is passed by the provisional legislature, and then immediately published in the SAR Gazette later that day, on the face of section 20(2), it may appear that the criminal provisions contained in that bill or ordinance will have effect from the beginning of July 1. It will, therefore, have retrospective effect.
However, this argument is fallacious. There are a number of ways to attack the argument. First, it appears there is a conflict between section 20(2) of the Interpretation and General Clauses Ordinance on one hand, and article 12 of the Bill of Rights, which is identical with article 15 of the ICCPR, on the other hand. If section 20(2) was enacted before BORO, then by ordinary operation of the common law or section three of the Bill of Rights, the former must be given a construction consistent with BORO, otherwise it is impliedly repealed. Section 20(2) must be interpreted so as to refer to publication on a day other than the day on which it was enacted.
If section 20(2) was enacted after the BORO, then the effect of the Letters Patent, and after July 1, article 39 of the Basic Law, is that the section must be interpreted in a way compatible with the ICCPR.