Players are required to register their decks and sideboards (if applicable) in Competitive and Professional Rules Enforcement Level tournaments. The Head Judge may require registration in Regular Rules Enforcement Level tournaments.
If a judge or Tournament Organizer wants to have decklists at Regular Rules Enforcement Level, the should make sure they inform the players as early as possible. If a judge or Tournament Organizer decides the event is serious enough to warrant decklists at Regular Rules Enforcement Level, however, they may want to instead change the Rules Enforcement Level to Competitive. Regular Rules Enforcement Level events with decklists are very rare.
Registered decklists record the original composition of each deck and sideboard (if applicable). Once your decklist has been accepted by a Tournament Official it may not be altered.
Altering a decklist after it has been accepted by a Tournament Official is not allowed because players might gain additional strategic information by waiting for a friend to help them decide what to play or by scouting opponents. A judge is allowed to alter the decklist when applying the fix for a Deck/Decklist Problem.
In Constructed tournaments, decklists must be submitted to a tournament official prior to the start of round 1, even if the player has an awarded bye for that round.
In Limited tournaments, decklists must be submitted prior to the start of the first round in which that player participates and does not have an awarded bye.
Constructed decklists need to be turned in before round 1 begins. Limited needs to be turned in before the first round the player is actually playing in begins. The difference here is that deck selection in constructed can vary much more based on scouting, and Sealed events typically require the deck to be built on site. This is going to be very rare outside of Grand Prix events where a large number of players will have byes for 1,2, or 3 rounds.
This rule is essentially what allows the sleep in special to exist! We may allow players to show up to limited Grand Prix events approximately the round before they are scheduled to play in order to construct their deck with plenty of time remaining. With Constructed events, they can easily turn in the list the night before.
Players have the right to request to see their decklist between matches. Such a request will be honored if logistically possible.
What is logistically possible is up to the judges at an event. Some event have thousands of decklists collected around the same time and trying to find one before they are organized might not be possible. If a player has alerted a judge to an error before he or she could gain advantage or before the event has begun, please be mindful of this information if unable to provide their list. Additionally, players will now often take a picture of their decklist once they have requested it, for their future use.
Generally, decklists are not public information and are not shared with other players during a tournament. At constructed-format, Professional Rules Enforcement Level tournaments (Pro Tour, World Magic Cup, World Championship, and Grand Prix), copies of opponents’ decklists will be provided to players in the single-elimination playoffs.
In the single-elimination playoffs of limited events, the chances of your opponent gaining information about your decklist are a lot smaller. As such, we only provide decklists for constructed-format events. Star City Games Open Series have also allowed Top 8 players to view the opponents decklists.
Note that while they have the decklist, it is considered to be notes taken outside of the game so players may only view them while in between games.