Does Magic the Gathering need an independent arbiter for reliable detection of cheating?

Question

In complete information games like chess, a player can always be certain about if and when an opponent cheats only given their own observations of the past and present state of the game because the decisions all players make (where to move a piece), and the board state are always fully public.

But Magic the Gathering has a lot of hidden state/information through zones like the library and hand, and mechanics like upside-down morph cards, which are only revealed later.

Do the game rules ensure that, at the very least when the game ends, each player knows for certain that the rules have been followed correctly - that no opponent cheated?

Which I could imagine happening through them manipulating hidden information in a way that is against the game's/cards' rules. Such as retrieving a card from their library that does not match the tutor's specifications (the tutors seem to require revealing the retrieved cards however, probably for this reason), or retroactively changing a decision to their advantage when it is revealed to the other player(s) (which might be prevented by making the player provably commit to it by writing their decision down)?

Do such situations actually exist which necessitate that an independent arbiter observes/tracks the game as well, so that evidence of the cheating does not get lost, and the matter of whether or not someone has cheated is adjudicated correctly?

If so, does the arbiter have to watch the entire game from both/all sides and note down every decision, or does the game ensure that they can always correctly reconstruct decisions once a player detects an incongruity, not using past observations?

Answer 1

Yes, but only to verify deck legality

During play, all printed cards (un-sets excluded, along with online-only cards) are worded in such a way that their effects can be verified by other players. Hackworth's answer goes into more detail here. It's very difficult to prove a negative, but I've never seen a card which was not designed this way.

However, that only guarantees that cards are resolved correctly. The game does not allow players to inspect their opponents deck to ensure that the deck itself is legal. There are several kinds of illegal deck (some could be more easily hidden than others):

• A deck with more than 4 copies of a vital card.
  • See this question for discussion of how this might be caught.
• A deck with fewer than the required number of cards (e.g. a 59-card deck in a 60-card format)
  • The number of cards in hidden zones is not hidden, so theoretically their opponent could ask them to count the cards in their library at the start of the game, which would expose the cheating.
• In constructed tournaments, players are required to use the same deck and sideboard for all games in the tournament, however, the lists are not revealed to their opponent. A player who swaps a few cards out (for example, someone who talks to their opponent's previous opponent to find out what kind of deck they're up against and then makes a few sideboard swaps before game 1) cannot be caught except by a judge.

Answer 2

Within the rules, the game does not need an arbiter. Cheating is another matter.

The rules of the game, together with the card designs, make sure that cards whose abilities affect the game state or have to fulfill certain criteria will at some point be visible to all players, if only at the end of the game. Some casual (not tournament-legal) game variants that put more emphasis on the social aspect of Magic might have exceptions, such as the Un-sets or certain multiplayer variants, but these are not discussed in the Comprehensive Rules that describe typical tournament formats.

For example, when a tutor effect allows you to search your library for a creature card and put it in your hand, you will always be required to reveal that card before you do that.

For another example, if you play a card as a 2/2 morph creature and that creature survives until the end of the game, it has to be revealed as the game ends to make sure you were allowed to play it as a morph.

708.9. If a face-down permanent or a face-down component of a merged permanent moves from the battlefield to any other zone, its owner must reveal it to all players as they move it. If a face-down spell moves from the stack to any zone other than the battlefield, its owner must reveal it to all players as they move it. If a player leaves the game, all face-down permanents, face-down components of merged permanents, and face-down spells owned by that player must be revealed to all players. At the end of each game, all face-down permanents, face-down components of merged permanents, and face-down spells must be revealed to all players.

That being said, rules violations both intentional and not do happen, of course. For that reason, each official tournament is required to have a Head Judge, an WotC-accredited person with sufficient knowledge of the game rules and tournament organization. The Head Judge assists players and ensure the orderly conduct of the tournament, including checking allegations of cheating, as described in the Magic Tournament Rules (MTR). The MTR further define the types of information in a game of Magic and how players are required to keep track of them.

This Head Judge requirement, however, is not part of the Comprehensive Rules that govern an individual game of Magic. Any game of Magic can correctly finish without any outside supervision at all. If cheating occurs, then the rules are not to blame, because by definition, they have been broken by the cheater.

Answer 3

Do the game rules ensure that, at the very least when the game ends, each player knows for certain that the rules have been followed correctly - that no opponent cheated?

The answer is "no". It's possible to break the rules and gain an unfair advantage, but the opponent has no way of telling without the intervention of an arbiter.

Example. One player cheats by playing more than 4 copies of a card. Opponent has no way to tell the player is cheating, since there are legal means through which the player can stop the opponent from seeing more than 4 copies of the card (even assuming his deck contains the cards necessary to see the opponent's deck/hand - many decks have no such tool).

Answer 4

Magic the Gathering has Judges, I'm one of them. No we don't watch the whole of every game, that would mean one judge for every two players and is just not possible when you have hundreds or thousands in some events. At later games in the finals when there are only a handful of tables left, then yes judges will watch games more closely. Usually we get called in when a player sees something they think is questionable.

There is a lot more that a judge can tell about what happened in a game than a lot of players think just by looking at game state and asking questions. Most of the time you can count cards and turns to see if any extra cards were drawn, can count game state on lands, and so many other things to verify a legal game state. Though we can look at your examples:

Retrieving a card from their library that does not match the tutor's specifications (the tutors seem to require revealing the retrieved cards however, probably for this reason)

Correct. Every single tutor that has any kind of restrictions on it either puts the card found into play (where it will be public, and thus revealed) or requires the player reveal the card they found before putting it in their hand or on top of their library to prove that it matches the restrictions. The only tutors that don't require revealing the card are ones like Demonic Tutor where there is no restrictions, so every card will be legal to find.

retroactively changing a decision to their advantage when it is revealed to the other player(s) (which might be prevented by making the player provably commit to it by writing their decision down)?

Magic does tend to avoid simultaneous decisions as much as it can to avoid scenarios like this, but when they do, yes, usually players make these decisions in some concrete way, for example with wheel of misfortune players often write their number down or choose it with hidden dice that they will reveal so it's hard to change when revealing.

Will this prevent every case of cheating, no, in a game of imperfect information it's pretty much impossible to prevent everything, even if someone is always watching. The game and tournament rules are set up as they are to try and limit cheating as much as possible, from your opponent always cutting your deck after shuffles, to the examples discussed. Independent arbiters for each just aren't feasible, most of the time between the rules structures and judges, it's not perfect but it's the best we really can have.

Answer 5

First of all, as mentioned, it's worth noting that one aspect of cheating (that is actually seen in chess tournaments) is whether there is any outside help, such as from an AI.

Ignoring that, then I believe the question is really whether or not someone can completely observe the game play to determine if there was any cheating.

In MtG, this is not initially the case, because there is information in the deck of cards that is hidden (such as number of cards, specific cards, etc..), but also allows for cheating by a clever card manipulator (such as not dealing from the top of the deck, etc.., improperly shuffling).

You could allow players to shuffle each other's decks to ensure they haven't "stacked" their deck in a specific way. That solves one possibility of cheating.

You can also solve the issue of deck construction and still have the contents of the deck initially unknown to the opposing player by using a cryptographic hash - i.e., once the deck is shuffled you come up with a text list of all the cards in order, then you come up with a public cryptographic hash of that list which can be known at the start of the game (without revealing the cards themselves). At the end of the game the players must reveal their private key for the cryptographic hash and then the card identity and order in the game can be confirmed.

Unfortunately the second technique conflicts with the first, unless you have an arbiter of some sort that can track the deck (and then you wouldn't need a hash). Of course - this arbiter could be automated, something that scans the deck after it's been shuffled and then this would be able to handle ensuring deck ordering in play (as well as construction).

But there's another form of cheating that you can't really discover by simply looking at the game play afterwards, and that's peeking. If the player is able to peek at their down cards (or yours) then that won't show up in the final game play.

There's certainly techniques you can use to minimize this type of cheating, but delve into magic (as in "tricks" instead of "the gathering") and you will be shocked with what is possible, including having rfid encoded cards that can be read by a palm reader/ring.

So, to answer your question in the end, MtG is not something where all forms of cheating can be determined by simply looking at the game play afterwards.

Though this is not fully true of chess anyways.