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Zimbabwe
Practice Relating to Rule 101. The Principle of Legality
Zimbabwe’s Constitution (1979), as amended to 2009, states:
THE DECLARATION OF RIGHTS
18 Provisions to secure protection of law
(5) No person shall be held to be guilty of a criminal offence on account of any act or omission that did not, at the time it took place, constitute such an offence, and no penalty shall be imposed for any criminal offence that is severer in degree or description than the maximum penalty that might have been imposed for that offence at the time when it was committed.
26 Interpretation and other savings
(7) No measures taken in relation to a person who is a member of a disciplined force of a country with which Zimbabwe is at war or with which a state of hostilities exists and no law, to the extent that it authorises the taking of such measures, shall be held to be in contravention of the Declaration of Rights. 
Zimbabwe, Constitution, 1979, as amended to 2009, Sections 18(5) and 26(7).
Zimbabwe’s Constitution (2013) states:
Chapter 4 – Declaration of Rights
69. Right to a fair hearing
(1) Every person accused of an offence has the right to a fair and public trial within a reasonable time before an independent and impartial court.
70. Rights of accused persons
(1) Any person accused of an offence has the following rights –
(k) not to be convicted for an act or omission that was not an offence when it took place;
(l) not to be convicted for an act or omission that is no longer an offence;
(n) to be sentenced to the lesser of the prescribed punishments if the prescribed punishment for the offence has been changed between the time the offence was committed and the time of sentencing.
86. Limitation of rights and freedoms
(2) The fundamental rights and freedoms set out in this Chapter may be limited only in terms of a law of general application and to the extent that the limitation is fair, reasonable, necessary and justifiable in a democratic society based on openness, justice, human dignity, equality and freedom, taking into account all relevant factors, including –
(b) the purpose of the limitation, in particular whether it is necessary in the interests of defence, public safety, public order, public morality, public health, regional or town planning or the general public interest;
(3) No law may limit the following rights enshrined in this Chapter, and no person may violate them –
(e) the right to a fair trial;
87. Limitations during public emergency
(1) In addition to the limitations permitted by section 86, the fundamental rights and freedoms set out in this Chapter may be further limited by a written law providing for measures to deal with situations arising during a period of public emergency, but only to the extent permitted by this section and the Second Schedule.
(4) No law that provides for a declaration of a state of emergency, and no legislative or other measure taken in consequence of such a declaration may –
(a) indemnify, or permit or authorise an indemnity for, the State or any institution or agency of the government at any level, or any other person, in respect of any unlawful act; or
(b) limit any of the rights referred to in section 86(3), or authorise or permit any of those rights to be violated. 
Zimbabwe, Constitution, 2013, Sections 69(1), 70(1)(k)–(l) and (n), 86(2)(b) and (3)(e), and 87(1) and (4).