Storybrook has no choice but to exist they cannot humanly produce all the goods they have so, they have contact with the outside world (we also saw Kathryn apply to Boston university and get accepted).
I think it’s just one of thoses cases of “small town law” the city take care of the smaller stuff by itself (disorderly conduct, petty theft and what not) and for the bigger crimes or issue they have to refer to higher authorities. The only thing is, those bigger issue, never really happened… once when thought they found a human hearth they said they would have to transfer MM to a state penitentiary so she can have a trial by jury (or something like that).
Isolated small town have a tendency to wanna stay that way…