The law came into effect as correctly stated in the above post of CTT's as a way to fight illegal gambling in Greece; most particularly, any form of entertainment that incorporated electrical or electronic parts was thus dubbed illegal, which was silly to no end, as even flipping a light switch could be considered illegal; unfortunately for the publicity of Greece, a tourist in Salonica was arrested for playing with the GameBoy brought along, a case that brings no end to our shame...
As people educated in law can more precisely explain to you, a law can only be overruled by another legal action, say, a decision in court (which acts as a sort of precedent in another case) or a new law that changes the previous law. What happened was that the law was proven to be illegal according to our constitution in court, which resulted in it being overruled in all legal cases from now on - as if it did not exist at all.