Possible Clues:

• Little League issue
• Restriction on children, maybe
• An Easter egg hunt may have one
• A casino may have one
• Maturity restriction
• 21, at a casino, say
• Restriction on Army enlistees
• I am the bees' knees joining a set that may bar older folk
• 12, for Little League World Series players
• The Senate has a lower one but not an upper one