Wizards of the Coast will change Magic: The Gathering tabletop legality rules for cards during a set’s release beginning with Phyrexia: All Will Be One.
Playing MTG cards in tabletop tournaments requires those cards to be legal within a specific format. Tabletop cards in the past were legal to play in sanctioned events following the global release of a set. But in recent months, WotC has altered when players can begin purchasing cards in bulk from local game stores, allowing sales to occur during prerelease events, which are now taking place before digital and global launches. This has led to some confusion as to when those cards are legal to play in a sanctioned tabletop tournament.