The U.N. Convention would make it harder for states to deport illegal immigrants who broke the law by entering the country.  States have the right to deport people who entered the country illegally, and the U.N. Convention would make that more difficult. The Convention gives extensive rights even to illegal immigrants, especially in the realm of the justice system (Article 17). Indeed, migrant activists often see deportation policies as immoral. Yet, a state has every right to arrest, imprison, and deport illegal immigrants. When an illegal immigrant commits a crime (in addition to unlawful entry into the country), states are often forced to pay to keep the criminal in prison, rather than deport him. The United States loses half-a-billion dollars each year this way. [1] Ultimately it's a matter of enforcing national laws, sovereignty, and the integrity of a nation's welfare-system.  [1] Colorado Alliance for Immigration Reform. "Economic costs of legal and illegal immigration." Accessed June 30, 2011.  .