A recent AP news story has indicated that the Obama administration is currently planning to deploy up to 1,500 National Guard volunteers to assist the U.S. military's counter-drug efforts along the U.S.-Mexico border. This comes amidst the ongoing debate about what is the proper role of the U.S. military on U.S. territory.
Many military researchers see deployment of U.S. troops as the only way to slow undocumented immigration, prevent terrorist infiltration, combat transnational drug gangs, and secure the nation. See the following reports:
U.S. Military Use Along the U.S.-Mexico Border
Role of the U.S. Military and Security Along the U.S.-Military Border
Legal Permissibility of Using Federal Troops on the Border
Others seriously question the legality of the deployment of U.S. troops on U.S. soil, citing the Posse Comitatus Act of 1878 which prevents the government's use of the U.S. military as a police force. These researchers also warn of the increasing militarization of the U.S.-Mexico border and doubt whether this will reduce undocumented immigration, curtail drug gang activity, or prevent terrorist entry into the United States. See the following report:
Creeping Militarization of the Home Front
Regarding President Obama's plans, deploying National Guard volunteers on U.S. soil does not violate the Posse Comitatus Act since these troops technically belong to the individual state where they serve and are therefore not 'federal troops'. Additionally, other researchers suggest that the Posse Comitatus Act needs modification in light of 21st century security realities. See this report:
Possee Comitatus, the Army, and Homeland Security: What Is the Proper Balance?
For neutral historical perspectives, see the following reports:
U.S. Army on the Mexican Border: A Historical Perspective
Posse Comitatus Act and the U.S. Army