In Starkey v Oklahoma Department of Corrections, the Oklahoma Supreme Court found that the Oklahoma Sex Offender Registration Act (SORA) is punitive or even intentional. Although the law in question was classified as non-retroactive, the Oklahoma Department of Corrections applied the new legislation retroactively. The court noted that “the retroactive application of the level allowance provisions of 57 O.S. Supp. 2007, 582.1 – 582.5 as amended by the Ministry violates the ex post facto clause”.  Retroactive legislation continuing what was perceived as a manifestly unethical means of tax avoidance was passed by the Fraser government in the early 1980s (see The Fund of Port Tax Avoidance). Similarly, legislation retroactively criminalizing certain war crimes has been found to be constitutional (see Polyukhovich v. Commonwealth). In Poland, the term lex retro non agit (“the law does not apply retroactively”) is used.  Lithuanian lawyer Dainius Žalimas claims that the Genocide Law (and later the articles of the Penal Code) were applied retroactively against participants in the Soviet crackdown on Lithuanian guerrillas and their supporters, citing examples of such decisions. Article 99 of the Criminal Code of the Republic of Lithuania was only introduced on 26 September 2000 and therefore cannot be used in the events of 1944-1953. Article 39 of the Constitution of Japan prohibits the retroactive application of laws. Article 6 of the Japanese Penal Code further stipulates that if a new law comes into force after the act has been committed, the lighter penalty must be imposed.
In Sweden, retroactive criminal sanctions and other retroactive legal effects of offences to which the State is entitled are prohibited under Article 10 of Chapter 2 of the Regeringsformen. Retroactive taxes or levies are not prohibited, but they can only go back retroactively to the time when a new tax law was proposed by the government. The retroactive effect of a tax or levy therefore extends from that moment until the bill is passed by Parliament. The sense that ex post facto laws violate natural rights is so strong in the United States that few, if any, state constitutions have failed to ban them. The Federal Constitution prohibits them only in criminal cases; But they are as unfair in civil matters as they are in criminal matters, and omitting a warning that would have been right does not justify the wrong thing. Nor should it be presumed that the legislature intended to use an expression in an unjustifiable sense if it could ever be burdened with the right thing by design rules. Adj. Reference to a court decision or law passed by a legislative body that would lead to its application to past transactions and legal actions. In criminal law, laws that would increase penalties or complicate previously legal criminal acts are prohibited by the constitutional prohibition of ex post facto laws (Article I, Section 9). Most court decisions that change the elements necessary to prove a crime or introduce evidence such as confessions are generally not issued retroactively to avoid a flood of motions from people convicted under previous rules.
Nor can laws or court decisions remove “acquired” property rights or modify contractual rights. However, some decisions are so fundamental to justice that they can have retroactive effect, depending on the balance between the stability of the law weighed against the common good. Retrospective is also called “retrospective”. (See: a posteriori) According to the first and second paragraphs of the 14th article of the Mexican Constitution, the retroactive application of the law is prohibited if it affects the rights of a person, but a new law can be applied if it benefits the person. An ex post-facto law (corrupted from Latin: ex postfacto, lit. “of the suite”) is a law that retroactively modifies the legal consequences (or status) of acts committed before the promulgation of the law or relationships that existed. .