Historical Rules · 7 February 2025
Rule 713.3
Official source text from the 7 February 2025 Rules release
If a substitute card is used in a deck, the card it represents is set aside prior to the beginning of the game (see rule 103.2a) and must remain available throughout the game. A substitute card can’t be included in a deck unless it is representing a double-faced card or a meld card.