Another key concern over children's rights arose in the late nineteenth century. Many children were working long hours in dangerous factories for very low pay. Employing children was common in the city, especially among poor immigrant populations. It was not until 1938 that Congress passed the Fair Labor Standards Act (FLSA) restricting child labor. The act continued to be the primary federal child labor law into the twenty-first century. Most states also passed child labor laws while other relied solely on the FLSA.
The limits imposed by the Fair Labor Standards Act are complex and dependent on the nature of the work and age of the youth. Children must be at least fourteen years of age to work in non-manufacturing jobs outside of school hours. They must be at least sixteen for general employment during school hours, and they must be eighteen to work in occupations considered hazardous by the Department of Labor, such as manufacturing of explosives, coal mining, logging, and driving a motor vehicle.
In some states, children must also have parental permission to work at certain jobs. Under some state laws, employers in certain businesses must obtain employment certificates from
the state to legally employ a youth under a certain age. On the other hand, parents cannot force minors to work in hazardous jobs. Criminal prosecution can result from violations of child labor laws, both involving employers and the parents depending on the specific case. Those convicted of child labor violations can be fined. An employer cannot use the defense of being ignorant of a youth's age if caught illegally employing a minor, even if the youth lied on his or her job application.