Which of the following terms refer to a law that allows individuals to be prosecuted for an action that, when committed, was not a crime, but was outlawed afterwards?

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.