Law shall have no retroactive effect?

Answer:
Law has prospective (forward-looking) effect only. The reason for this is that people are entitled to have advance knowledge of the legality or illegality of their behavior before they engage in it. It is similar in theory to the Constitutional prohibition against ex post facto laws.
First answer by Anacanapanastan. Last edit by Anacanapanastan. Contributor trust: 200 [recommend contributor recommended]. Question popularity: 2 [recommend question].