At the dawn of the Magic era, card sleeves existed for the storage and display of collectable cards. The idea that cards will retain a collectable value while also being played was revolutionary. Most early players refused to sleeve their cards. Sleeves available at the time fell into two categories: “penny” sleeves-- cheap, flimsy, and thin, and “top-loaders”-- two rigid plastic sheets bound together. In 1995 Ultra-PRO became the first company to sell card sleeves specifically designed for use during game play.
Today card sleeves enjoy universal appeal. An ever-increasing kaleidoscope of color, texture, and effects has supplanted the completely clear sleeves of 1995. Whether printed today or in 1993, Magic the Gathering cards can be safely played in their plastic protectors. However, players must be careful that their sleeves choice does not hinder their game play, and judges must be vigilant about making sure that sleeves not reveal the cards they protect.
Here is what the DCI officially has to say about sleeves:
[Universal Tournament Rules]
35. Card Sleeves
Players may use plastic card sleeves or other protective devices on cards. If a player chooses to use card sleeves, all cards in the player’s current deck must be placed in the sleeves in an identical manner. If the sleeves feature holograms or other similar markings, cards must be inserted into the sleeves so these markings appear only on the face of the cards.
Once a match begins, a player may request that the judge inspect an opponent’s card sleeves. The judge may disallow a player’s card sleeves if the judge believes they are marked, worn, or otherwise in a condition or of a design that interferes with shuffling or game play. To avoid confusion, a card sleeve may also be used to mark a player’s card if the card is in an opponent’s playing area.
Though originally viewed separately from the cards, sleeves are now considered a part of the card. Thus, if the sleeve is marked, so is the card. Additionally, if a sleeves is transparent or translucent (partially see-through), then the card inside the sleeve must not have any distinguishing marks or discoloration. Playing a worn card in a colored translucent sleeve doesn’t matter if you can still see the wear.
When inspecting a deck, special attention should be paid to the back of the sleeves. Common problems are finger marks from riffle shuffling, bent corners, tears, creases, and dirt-- these are all related to play wear. Less common problems occur with discoloration, rippling, and uneven sleeve length. These are usually problems with the manufacturing process or materials. In all cases, if the sleeves are not uniform, then some action must be taken. If the marking has a pattern, action should be immediate. If the markings are believed to be intentional, then penalties for marked cards as well as cheating should be applied.
No single sleeve make or model is disallowed by the DCI. Local and regional tournament organizers do commonly ban particular colors or styles of sleeves from their event to reduce the likelihood of abuse. The most commonly banned sleeves fall into two categories: reflective and holographic.
Even a little information is too much
Reflective sleeves allow a player to discern information about a card by using a slight tilt to see the reflection off another card-- usually the top card of the deck reflecting off the next card down. Even something as simple as distinguishing land or non-land based on card frame color is cheating.
The most commonly available reflective sleeves are the Ultra-Pro: Metalized. The dark colors tend not to give away information, but the silver and gold are too reflective for most tournament play.
Holographic sleeves have designs on the sleeve that obstruct the readability of the card inside. Holographic sleeves are acceptable if the design is on the back of the card, and the front is transparent. Otherwise, it is difficult for opponents and tournament staff easily to determine what each card is. Most players do not realize the disruption caused by these holograms. A polite request to change the sleeves or perhaps a more stern warning for unsportsmanlike conduct should be the worst that even happens in these cases.
The most commonly available holographic sleeves are the KMC / Card Barrier Series: Super Holography and the Player's Choice: Holographic series.
So pretty you can't see the cards.
Evaluating new types
Evaluating new and existing sleeve types is simple:
1) When face up on the table, is the card readily identifiable sitting across from the player?
Obscured art and text is why sleeves with holographic fronts are frequently disallowed at sanctioned events.
2) If a card is tilted up from the deck without showing the face, can any information been learned from the reflection off the back of the card below?
This is why the highly reflective silver and gold metal sleeves are often disallowed but the darker metalized sleeves are okay.
Using these two questions it should be easy to evaluate any new sleeve variants that come on the market.
One recommended course of action before and event is talk to the dealers. Look at all the sleeves they have available. If they have ones that are unacceptable, ask them not to sell those specific sleeves. Dealers will generally cooperate because they can assure players that the remaining stock should pose no problems.