The standard definition used to describe and define human trafficking is authored by the United Nations. Crossing borders is not a requisite to be considered human trafficking; therefore, domestic prostitution that meets the criteria of the Palermo Protocol is human trafficking.
PROTOCOL TO PREVENT, SUPPRESS AND PUNISH TRAFFICKING IN PERSONS, ESPECIALLY WOMEN AND CHILDREN, SUPPLEMENTING THE UNITED NATIONS CONVENTION AGAINST TRANSNATIONAL ORGANIZED CRIME
Author: United Nations
Article 2
Statement of purpose
The purposes of this Protocol are:
(a) To prevent and combat trafficking in persons, paying particular attention to women and children;
(b) To protect and assist the victims of such trafficking, with full respect for their human rights; and
(c) To promote cooperation among States Parties in order to meet those objectives.
Article 3
Use of terms
For the purposes of this Protocol:
(a) 'Trafficking in persons' shall mean the recruitment, transportation, transfer, harbouring or receipt of persons, by means of the threat or use of force or other forms of coercion, of abduction, of fraud, of deception, of the abuse of power or of a position of vulnerability or of the giving or receiving of payments or benefits to achieve the consent of a person having control over another person, for the purpose of exploitation.
Exploitation shall include, at a minimum, the exploitation of the prostitution of others or other forms of sexual exploitation, forced labour or services, slavery or practices similar to slavery, servitude or the removal of organs;
(b) The consent of a victim of trafficking in persons to the intended exploitation set forth in subparagraph (a) of this article shall be irrelevant where any of the means set forth in subparagraph (a) have been used;
(c) The recruitment, transportation, transfer, harbouring or receipt of a child for the purpose of exploitation shall be considered 'trafficking in persons' even if this does not involve any of the means set forth in subparagraph (a) of this article;
(d) 'Child' shall mean any person under eighteen years of age.
Copied from the website of the Coalition Against Trafficking in Women International where the complete Palermo Protocol agreement and many other resources are available : http://action.web.ca/home/catw/readingroom.shtml?x=16846