If there are no cards in a player’s library and an effect offers that player the choice to draw a card, that player can choose to do so. However, if an effect says that a player can’t draw cards and another effect offers that player the choice to draw a card, that player can’t choose to do so.
September 30, 2011 · Innistrad
If a permanent has both a +1/+1 counter and a -1/-1 counter on it, N +1/+1 and N -1/-1 counters are removed from it as a state-based action, where N is the smaller of the number of +1/+1 and -1/-1 counters on it. See rule 704.
June 17, 2011 · Commander 2011
If a permanent has both a +1/+1 counter and a -1/-1 counter on it, N +1/+1 and N -1/-1 counters
May 1, 2011 · New Phyrexia
If a permanent has both a +1/+1 counter and a -1/-1 counter on it, N +1/+1 and N -1/-1 counters are removed from it as a state-based action, where N is the smaller of the number of +1/+1 and -1/-1 counters on it. See rule 704.
April 1, 2011 · Duel Decks: Knights vs. Dragons
If a permanent with an ability that says it can't have more than N counters of a certain kind on it has more than N counters of that kind on it, all but N of those counters are removed from it as a state-based action. See rule 704.
February 4, 2011 · Mirrodin Besieged
If a permanent with an ability that says it can’t have more than N counters of a certain kind on it has more than N counters of that kind on it, all but N of those counters are removed from it as a state-based action. See rule 704.
October 1, 2010 · Scars of Mirrodin
If a permanent with an ability that says it can’t have more than N counters of a certain kind on it
July 16, 2010 · Magic 2011
If a permanent with an ability that says it can't have more than N counters of a certain kind on it has more than N counters of that kind on it, all but N of those counters are removed from it as a state-based action. See rule 704.