A player may activate a loyalty ability of a permanent they control any time they have priority and the stack is empty during a main phase of their turn, but only if no player has previously activated a loyalty ability of that permanent that turn.
September 30, 2011 · Innistrad
A player may activate a loyalty ability of a permanent he or she controls any time he or she has priority and the stack is empty during a main phase of his or her turn, but only if no player has previously activated a loyalty ability of that permanent that turn.
June 17, 2011 · Commander 2011
A player may activate a loyalty ability of a permanent he or she controls any time he or she has
February 4, 2011 · Mirrodin Besieged
A player may activate a loyalty ability of a permanent he or she controls any time he or she has priority and the stack is empty during a main phase of his or her turn, but only if no player has previously activated a loyalty ability of that permanent that turn.
October 1, 2010 · Scars of Mirrodin
A player may activate a loyalty ability of a permanent he or she controls any time he or she has
February 1, 2010 · Worldwake
A player may activate a loyalty ability of a permanent he or she controls any time he or she has priority and the stack is empty during a main phase of his or her turn, but only if no player has previously activated a loyalty ability of that permanent that turn.