After the Keating-Owen Child Labor Act of 1916, How Did

After the Keating-Owen Child Labor Act of 1916, how did the Supreme Court argue that the federal government could not regulate child labor?

A) Child labor occurs at the manufacturing level, rather than the commerce level, thus leaving the issue to the states.
B) Child labor is a family financial issue, thus leaving the issue to individual rights.
C) Child labor is a family financial issue, thus leaving the issue to the states.
D) Child labor relates to commerce, rather than manufacturing, thus leaving the issue to individual rights.