Make up a new word and fine them all the same. If you engage in anti consumer practices then I, a consumer, highly endorse anti corporate legislation.
Fining them for things they do now before such law exists, however, should not be pursued. Ex post acte law is forbidden in large parts of the world for good reason.
https://en.wikipedia.org/wiki/Ex_post_facto_law:
Ex post facto criminalization is also prohibited by Article 7 of the European Convention on Human Rights, Article 15(1) of the International Covenant on Civil and Political Rights, and Article 9 of the American Convention on Human Rights. While American jurisdictions generally prohibit ex post facto laws, European countries apply the principle of lex mitior ("the milder law"). It provides that, if the law has changed after an offense was committed, the version of the law that applies is the one that is more advantageous for the accused. This means that ex post facto laws apply in European jurisdictions to the extent that they are the milder law.