Magic: The Gathering Comprehensive Rules Changes - Core Set - Ninth Edition to Ravnica: City of Guilds

Old rule (Core Set - Ninth Edition)	New rule (Ravnica: City of Guilds)
419.5b. [Click to view all changes.]
419.5b. Some abilities read, "Whenever [X], you may [Y]. If you do, [Z]." The "if you do" clause refers to choosing to do the event Y, regardless of what events actually occur as a result of that decision. If Y is replaced entirely or in part by a different event, the "if you do" clause refers to the event that replaced Y.	419.5b. Some abilities read, "you may [X]. If you do, [Y]." An "if you do" clause that follows an "if you may [X]" clause refers to choosing to do the event X, regardless of what events actually occur as a result of that decision. If X is replaced entirely or in part by a different event, the "if you do" clause refers to the event that replaced X.

Old rule (Core Set - Ninth Edition)

New rule (Ravnica: City of Guilds)

419.5b.

Some abilities read, "Whenever [X], you may [Y]. If you do, [Z]." The "if you do" clause refers to choosing to do the event Y, regardless of what events actually occur as a result of that decision. If Y is replaced entirely or in part by a different event, the "if you do" clause refers to the event that replaced Y.

419.5b.

Some abilities read, "you may [X]. If you do, [Y]." An "if you do" clause that follows an "if you may [X]" clause refers to choosing to do the event X, regardless of what events actually occur as a result of that decision. If X is replaced entirely or in part by a different event, the "if you do" clause refers to the event that replaced X.