NRA
The Federal government sets specific labor laws, including those about child labor. But the states can put their own laws in effect, as long as they do not contradict the Federal laws. Most states regulate the hours a child can work and the ages they can get a work permit.
Department of Labor
The Federal Government
Noise Control Act
The Fair Labor Standards Act (FLSA) sets federal minimum wage, overtime pay, recordkeeping, and youth employment standards. Its purpose is to protect workers by ensuring fair compensation for work, regulating working hours, and prohibiting oppressive child labor practices.
Wage and Hour Division
Generally speaking, it's always the best policy to keep a child safe when the child has a part in a film. The Screen Actor's Guild sets child standards, even if the child/parents are not members. If a parent believes the child is still not protected by SAG, they can make private arrangements with the film's director of the producer.
regulated federalism
Wage and Hour Division
The Department of Labor (DOL) sets the overtime pay standards and minimum pay rates. The DOL would be the best place to find information, by state, regarding what is legal and what is not legal, in regards to labor.
Wage and Hour Division
The W3C