601.2. Card Legality
601.2.a. A card may only be included in a deck if it is from a set that is legal in that format or it has the same name as a card from a set that is legal in that format.
601.2.b. Until set release parity is reached, regional limitations on the legality of cards will be enforced according to the official product launch date in the region where an event is being held.
601.2.c. If an existing card is reprinted in a new set, but its collector number is not within the normal numbering of that set, it does not affect the card's format legality.
601.2.c.1. Example: A card with collector number 300/250 is not automatically legal within the standard format of that set.