Why is the entertainment industry exempt from the Fair Labor Standards Act? I have no idea how to research this question. edit: I mean, I thought the constitution specifies that laws shall be equally enforced.
There is a specific exemption in 29 USC 213(c)(3) that
The provisions of section 212 of this title relating to child labor shall not apply to any child employed as an actor or performer in motion pictures or theatrical productions, or in radio or television productions.
a condition of employment under which (1) any employee under the age of sixteen years is employed by an employer (other than a parent or a person standing in place of a parent employing his own child or a child in his custody under the age of sixteen years in an occupation other than manufacturing or mining or an occupation found by the Secretary of Labor to be particularly hazardous for the employment of children between the ages of sixteen and eighteen years or detrimental to their health or well-being) in any occupation, or (2) any employee between the ages of sixteen and eighteen years is employed by an employer in any occupation which the Secretary of Labor shall find and by order declare to be particularly hazardous for the employment of children between such ages or detrimental to their health or well-being; but oppressive child labor shall not be deemed to exist by virtue of the employment in any occupation of any person with respect to whom the employer shall have on file an unexpired certificate issued and held pursuant to regulations of the Secretary of Labor certifying that such person is above the oppressive child-labor age. The Secretary of Labor shall provide by regulation or by order that the employment of employees between the ages of fourteen and sixteen years in occupations other than manufacturing and mining shall not be deemed to constitute oppressive child labor if and to the extent that the Secretary of Labor determines that such employment is confined to periods which will not interfere with their schooling and to conditions which will not interfere with their health and well-being.
Without the statutory exemption, if you are under 16 and employed by a non-parent, in any occupation, that is oppressive child labor. But because of the specific exemption, what would otherwise be statutorily oppressive child labor is allowed.
The political "why" question (why did the bill contain such language) is extremely difficult to answer. The only substantive clues that I have seen are in a 1959 dissertation by G.E. Paulsen and this article on the passage of the act. It seems to be a legislative compromise relating stricter original standards, and was particularly driven by the need to allow children to work on family farms. The relevant clause was added from the floor of the House on May 24, 1938 by Rep Charles Kramer (CA). This is recorded on p. 7441 of the Congressional Record, which, unfortunately, is not freely available online. The two toughest questions were asked by Schneider (WI), Kramer's reply in parentheses:
The gentleman's amendment would exempt children engaged only in the making of moving pictures? (The gentleman is correct) There are very few young people employed in that occupation? (Very few. There are hardly more than 10 employed at one time.)
Shirley Temple was in fact invoked by Kramer.