Human Trafficking is the illegal trade of persons in a position of vulnerability by means of force or coercion for purpose of exploitation. It is claimed by some to be the second-largest criminal industry in the world. Trafficking is distinguished, theoretically, from human smuggling in that the element of exploitation is missing from the latter. In practice, this distinction has proven problematic in many cases.
In 2000, the United Nations opened for signature the Palermo Protocol to Prevent, Suppress and Punish Trafficking in Persons, especially Women and Children.  which came into force on December 23, 2003. This was the first time the issue of human trafficking was addressed on an international level and came after identification of the phenomenon by the International Organization for Migration (IOM) in the late 1990s. The Protocol currently has 146 countries plus the European Community as signatories, acceptances or ratifications of the Protocol.
Trafficking is expansively defined in the UN Protocol as:
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. ...The consent of a victim of trafficking in persons to the intended exploitation... shall be irrelevant where any of the means set forth (above) have been used. The recruitment, transportation, transfers... 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 (above).
- Protocol to Prevent, Suppress and Punish Trafficking in Persons Especially Women and Children, supplementing the United Nations Convention against Transnational Organized Crime (Trafficking Protocol), adopted November 15, 2000, G.A. Res. 55/25, annex II, 55U.N. GAOR Supp. (No.49) at 60, U.N. Doc. A/45/49 (Vol.I) (2001)