Human Trafficking Laws
Since the date of the episode, the US Federal Government passed the The Victims of Trafficking and Violence Prevention Act (TVPA) which forms 22 U.S. Code Chapter 78 which makes it unlawfull to "traffic in" (buy or sell) human beings, particualrly for sexual purposes. According to "Human Trafficking State Laws":
In 2003, Washington became the first state to criminalize human trafficking. Since then, every state has enacted laws establishing criminal penalties for traffickers seeking to profit from forced labor or sexual servitude. The laws vary in several ways including who is defined as a “trafficker,” the statutory elements required to prove guilt in order to obtain a conviction and the seriousness of the criminal and financial penalties those convicted will face.
But none of those laws was in effect during the 1990s.
Thirteenth Amendment
Whether a prosecution could have been brought brought directly under the 13th amendment to the US Constitution is not entirely clear to me. Bailey v. Alabama, 219 U.S. 219 (1911) held that the 13th Amendment was self-executing:
[219 U. S. 240] Pursuant to the authority thus conferred [by section 2 of the 13th amendment], Congress passed the Act of March 2, 1867, c. 187, 14 Stat. 546, the provisions of which are now found in §§ 1990 and 5526 of the Revised Statutes, as follows:
SEC. 1990. The holding of any person to service or labor under the system known as peonage is abolished and forever prohibited in the Territory of New Mexico, or in any other territory or state of the United States; and all acts, laws, resolutions, orders, regulations, or usages of the Territory of New Mexico, or of any other territory or state, which have heretofore established, maintained, or enforced, or by virtue of which any attempt shall hereafter be made to establish, maintain, or enforce, directly or indirectly, the voluntary or involuntary service or labor of any persons as peons, in liquidation of any debt or obligation, or otherwise, are declared null and void.
SEC. 5526. Every person who holds, arrests, returns, or causes to be held, arrested, or returned, or in any manner aids in the arrest or return, of any person to a condition of peonage, shall be punished by a fine of not less than one thousand nor more than five thousand dollars, or by imprisonment not less than one year nor more than five years, or by both.
...
[219 U. S. 241] The plain intention was to abolish slavery of whatever name and form and all its badges and incidents; to render impossible any state of bondage; to make labor free, by prohibiting that control by which the personal service of one man is disposed of or coerced for another's benefit, which is the essence of involuntary servitude.
While the Amendment was self-executing so far as its terms were applicable to any existing condition, Congress was authorized to secure its complete enforcement by appropriate legislation. As was said in the Civil Rights Cases 109 U.S. 20:
By its own unaided force and effect, it [the 13th amendment] abolished slavery and established universal freedom. Still, legislation may be necessary and proper to meet all the various cases and circumstances to be affected by it and to prescribe proper modes of redress for its violation in letter or spirit. And such legislation may be primary and direct in its character, for the amendment is not a mere prohibition of state laws establishing or upholding slavery, but an absolute declaration that slavery or involuntary servitude shall not exist in any part of the United States.
Peonage Abolition Act of 1867
The Court in Bailry cites the The Peonage Abolition Act of 1867 which made it a crime to hold any person in "voluntary or involuntary service or labor of any persons as peons, in liquidation of any debt or obligation, or otherwise" This law would, it seems to me, have been able to be applied to the case described in the question, but it was more usually applied to agricultural labor, and it might well be that no one would have thought to apply it. The first part of this law became 42 USC 1994 and the second 18 USC 1581.
Findlaw's page on the 13th Amendment also quotes the Civil Rights Cases 109 U.S. 3, 20 (1883):
This Amendment is undoubtedly self-executing without any ancillary legislation, so far as its terms are applicable to any existing state of circumstances. By its own unaided force and effect it abolished slavery, and established universal freedom.
The Findlaw page goes on to say that:
The force and effect of the Amendment itself has been invoked only a few times by the Court to strike down state legislation which it considered to have reintroduced servitude of persons, and the Court has not used section 1 of the Amendment against private parties. In 1968, however, the Court overturned almost century-old precedent and held that Congress may regulate private activity in exercise of its Section 2 power to enforce section 1 of the Amendment.{Jones v. Alfred H. Mayer Co., 392 U.S. 409, 439 (1968) [in Fiindlaw's footnote 27]}
The Peonage Abolition Act was also extensively refereed to in Pollock v. Williams 322 U.S. 4 (1944) where the Court wrote, in section 22 of the opinion:
he undoubted aim of the Thirteenth Amendment as implemented by the Antipeonage Act was not merely to end slavery but to maintain a system of completely free and voluntary labor throughout the United States. ... Congress has put it beyond debate that no indebtedness warrants a suspension of the right to be free from compulsory service.
Mann Act
The Mann Act (18 U.S.C. § 1581) prohibited transporting people across state lines for prostitution (originally only women), but no state line is stated to have been crossed in the question. Nor does it seem that selling a child for non-sexual labor fit the terms of the Mann Act.
Child Endangerment Law
The New York State Penal Law Article 260, Section 260.10 provides that:
A person is guilty of endangering the welfare of a child when:
- He or she knowingly acts in a manner likely to be injurious to the physical, mental or moral welfare of a child less than seventeen years old or directs or authorizes such child to engage in an occupation involving a substantial risk of danger to his or her life or health; or
- Being a parent, guardian or other person legally charged with the care or custody of a child less than eighteen years old, he or she fails or refuses to exercise reasonable diligence in the control of such child to prevent him or her from becoming an "abused child," a "neglected child," a "juvenile delinquent" or a "person in need of supervision," as those terms are defined in articles ten, three and seven of the family court act.
It would seem that in the circumstances discussed in the question, the drug dealer could have been prosecuted under 260.10(1) and the mother under 260.10(2). It is hard to see how an experienced prosecutor would have overlooked this law.