For the US apparently the following is the operating Supreme Court precedent. Ex post facto criminal laws are banned, but not civil laws. https://www.law.corne

For the US apparently the following is the operating Supreme Court precedent. Ex post facto criminal laws are banned, but not civil laws. https://www.law.cornell.edu/constitution-conan/article-1/section-9/clause-3/retroactive-taxes-and-ex-post-facto-laws https://www.law.cornell.edu/constitution-conan/article-1/sec... > The Supreme Court has generally rejected ex post facto challenges to laws imposing retroactive tax liability.1 In Kentucky Union Co. v. Kentucky, the Court emphasized that not all retroactive laws are ex post facto, as the prohibition on ex post facto laws applies only to retroactive criminal laws.2 The majority further opined: “Laws of a retroactive nature, imposing taxes or providing remedies for their assessment and collection, and not impairing vested rights, are not forbidden by the Federal Constitution.” 3