According to the UN Protocol against the Smuggling of Migrants by Land, Sea and Air, "Smuggling of migrants" means the procurement, in order to obtain, directly or indirectly, a financial or other material benefit, of the illegal entry of a person into a State Party of which the person is not a national or a permanent resident.

An individual may voluntarily engage the services of a smuggler, but increasingly be drawn into a web of exploitative relationships in order to pay off the debts they incurred in the process. If the individual falls into a situation of debt bondage, it can become a case of human trafficking.