Sleeves have gone from protective coverings for valuable collectables to highly stylized play accessories. Companies like UltraPro now have hundreds of colors, textures, materials, designs, and art for players to add flare, individuality, and panache to their play environment, displaying their favorite characters, anime, games, and fantastic art.
The DCI does not have rules regarding the allowance or restriction of specific sleeves. The DCI does have rules against sleeves or cards marked accidentally through use or intentionally to cheat. We understand that due to manpower and competitive levels of play an organizer or head judge may restrict some general classes of sleeves from use. What follows is philosophy on what factors judges and organizers should use in making their decision to disallow an entire class of sleeves from their event.
The three primary factors restricting any sleeve are the difficulty to check for markings, the difficulty in reading the card from across the table, and highly reflective "mirror" or "metalized" sleeves due to the ability to reveal the face of the card. Holographic sleeves that make a card's face difficult to read from across the table generally are not used in tournaments. Mirror or metalized sleeves are generally only allowed at the most casual of events. The art factor, where the art on some sleeves may make them stand out or hide markings, is mitigated by the rules enforcement level (REL) of the event and the number of staff available to conduct deck checks.
Regular level events should allow nearly all types of sleeves. These events rarely use deck verification and if deck checks are not used, then all non-reflective sleeves should be allowed. These events also rarely have the significant prizes which a player might risk marking their sleeves to obtain. Regular-level events that do have deck checks and do have significant prizes, though, rarely have more than two officials, taking up too much time to carefully check art that goes entirely to the border of the sleeve or highly complex art and patterns on sleeves – and thus these types of sleeves may be disallowed.
Competitive events generally require deck checks but also generally have more staffing. Though a significant prize is often awarded at Competitive events, the types of sleeves used are still varied, normally excluding only mirrored sleeves or sleeves which have a border that isn't a universal color – for instance, when the art on the sleeve touches the edges. Because these events generally have more staff they can allow complex art, so long as the edges are universal in color. Having universal edges, a player cannot easily hide marks on the sleeves that can be seen when the cards are in a pile.
Professional-level events are the most restrictive environment for sleeves. Professional events offer sizeable cash awards and players travel thousands of miles to these events. The players expect higher adherence to many procedures that a Regular event may not even perform and increased restrictions on their behavior. Sleeves at these events are restricted to monocolored art that doesn't come to the edge, a uniform sleeve color, and non-reflective backs. Magic: the Gathering logo sleeves are allowed even at Magic's Pro Tour and World Championship tournaments because they are produced at high quality with consistent placement of a single-color art and a low-reflective finish.
Sleeves are growing in variety and use, but their quality is also improving. When looking at disallowing a category of sleeves, be as flexible as the level of the event will allow. Players dislike feeling over-policed or forced to buy new sleeves on site when the rationale behind banning a class of sleeve is not understood or inconsistent. Why would a class of sleeve be useable at a Pro Tour Qualifier and not be useable at Friday Night Magic less than a week later?
Other important articles on sleeves can be found in the Judge Article Archives as well.