As a common rule, law does not apply to the past. This is what jurists have called the "Principle of Non-Retroactivity of Law". The essence of this principle implies that a law’s effect does not extend to include past affairs and cannot pass judgment on events which occurred prior to its implementation. Instead, a law only applies to events that occur after its implementation. Thus, the date of implementation is a decisive factor in determining a law's applicability. All laws become applicable after their publication in the Official Gazette unless there is a stipulation to the contrary. Article No. (71) of the Saudi Arabian Basic Law stipulates, "Regulations shall be published in the official gazette and shall be effective from the date of their publication unless there is a statement to the otherwise." For instance, the latest amendments to the Saudi Work Law were published in the Official Gazette on 5/6/1436H. However, it stated that the effective date would begin on 1st Muharram 1437H. As such, all events which occurred prior to the implementation of the law are not subject to its provisions. On the contrary, all events which took place after the law has been implemented are subject to its authority.
Legal provisions do not last forever. Instead, there is a specific time span to be applied which is the period extending from the date of its implementation to the date of its nullification. This should not be overridden unless the public interest so requires.
The notion of non-retroactivity of law has been established for the sake of public protection. Nonetheless, there can be exceptions, e.g. when the new law is favorable to an accused individual. In cases when the law states the nullification of the crime or mitigates the punishment, it would be in the interest of the accused parties to apply the law retroactively despite the fact that their crimes had been committed in the past.
Yet, if we consider the position of the Islamic Shari'a, from the standpoint of non-retroactivity of law and the associated exceptions, we notice that the ancient jurists were aware of this theory. Indeed, the Islamic Shari'a had come long before the man-made laws in ratifying the contents of this principle. It is believed that the principle under review contains a considerable degree of justice and logic. This is why contemporary jurists have chosen such a name and merged it into Islamic jurisprudence.