Each individual Little League has a set of regulated boundaries that specify which children are eligible to register with their league. These boundaries help maintain a sense of community by grouping kids of nearby neighborhoods or by which schools they are enrolled.

League Eligibility is determined by three main rules:

1. Kids whose primary residence is within the local league’s boundary can play for that hometown league.
2. Kids can play for the league where their school is located.
3. Kids from divided homes may choose to play in a league in whose boundaries either parent resides.

There is a waiver process for a few exceptions to the above rules, like players who were previously enrolled in the league having later moved outside the boundaries.
 
For more information, see the Little League website: Little League Boundaries - What Parents Need to Know

In the map below, Petaluma Valley Little League is the Royal (lighter) blue, Petaluma American is the Navy (darker) blue, and Petaluma National is red.