I want to know the answer to the following question:
What new rule was put into practice during the 2010-11 season?
All the background I'm provided with is that "As of the 2010–11 season, the Premier League introduced new rules mandating that each club must register a maximum 25-man squad of players aged over 21, with the squad list only allowed to be changed in transfer windows or in exceptional circumstances.". Is that enough to answer the question?