The phrase "retroactive effect" means something that is applied or enforced to past events or actions, even if it was decided or made after those events occurred. Full definition
The current government of the Catalonian Autonomous Comunity has been anouncing project of laws with retroactive effects like the cancelation of the Catalonian Debt, Census projects, etc.. (politics.stackexchange.com)
2016 Corporations Code amendment given retroactive effect to revive rights, powers and privileges of 2014 cancelled Limited Liability Company. (romalaw.com)
The court also held that the increase in maximum term for the offence did not have retroactive effect for the purpose of the s. 36 definition. (practicepro.ca)