Unfortunately the specific answer to your question is "yes, but it depends on the state""yes the law might forbid children from being out and about without supervision, but it depends on the state". ForI believe the section of law most applicable to this question is "child neglect", and for the most part the definitions of child neglect are left to the states, generally 'neglect' would, I believe, be the charge. There is a very wide variety in what is considered "neglect" in various states.
To stick with Maryland again (just to have an example), therethis is also the definition of neglect from 5-701
The department of health and human services provides a rather nice summary of state laws as they apply to neglect (mixed amongand many other crimes against children): https://www.childwelfare.gov/systemwide/laws_policies/statutes/define.pdf . They really do run the gamut as a judge could potentially apply them to 'free range children':
(I have edited the quotes from the above-linked pdf only to remove definitions irrelevant to the discussion... but please note that all of them have been edited, and should not be represented as accurateauthoritative summaries of the referenced statutes)