423.1. Players are responsible during competitions to make sure their cards and/or sleeves are not marked.
423.2. Marked is defined as bearing something that makes it possible to identify the card without seeing its face.
423.3. If cards are sleeved, they should be inspected for marking while in the sleeves.
423.4. Judges may ask players to remove sleeves or replace any specific sleeve at any time during a competition.