“The military generally provides support to law enforcement and immigration authorities along the southern border. Reported escalations in criminal activity and illegal immigration, however, have prompted some lawmakers to reevaluate the extent and type of military support that occurs in the border region… Addressing domestic laws and activities with the military, however, might run afoul of the Posse Comitatus Act [U.S. Code, Title 18, § 1385], which prohibits use of the armed forces to perform the tasks of civilian law enforcement unless explicitly authorized…
After the attacks of September 11, 2001, military support was expanded to include counterterrorism activities. Although the DOD [Department of Defense] does not have the ‘assigned responsibility to stop terrorists from coming across our borders,’ its support role in counterdrug and counterterrorism efforts appears to have increased the Department’s profile in border security.”