This details the laws of use of the military and the primary laws for building the Wall by the military. Should Trump declare a crisis and use the military to build the wall these laws will be the ones eventually going to the Supreme Court. Border Security and Military Support: Legal Authorizations and Restrictions Restrictions The primary restriction on military participation in civilian law enforcement activities is the Posse Comitatus Act (PCA).9The PCA prohibits the use of the Army and Air Force to execute the domestic laws of the United States except where expressly authorized by the Constitution or Congress. The PCA has been further applied to the Navy and Marine Corps by legislative and administrative supplements. For example, 10 U.S.C. §375, directs the Secretary of Defense to promulgate regulations forbidding the direct participation "by a member of the Army, Navy, Air Force, or Marines in a search, seizure, arrest, or other similar activity" during support activities to civilian law enforcement agencies. DOD issued Directive 5525.5, which outlines its policies and procedures for supporting federal, state, and local LEAs. According to the Directive, the following forms of direct assistance are prohibited: (1) interdiction of a vehicle, vessel, aircraft, or other similar activity; (2) a search or seizure; (3) an arrest, apprehension, stop and frisk, or similar activity; and (4) use of military personnel in the pursuit of individuals, or as undercover agents, informants, investigators, or interrogators. It is generally accepted that the PCA does not apply to the actions of the National Guard when not in federal service.10 As a matter of policy, however, National Guard regulations stipulate that its personnel are not, except for exigent circumstances or as otherwise authorized, to directly participate in the arrest or search of suspects or the general public.11 12 The Constitution, however, contains no provision expressly authorizing the President to use the military to execute the law. The question of whether the constitutional exception includes instances where the President is acting under implied or inherent constitutional powers is one the courts have yet to answer. DOD regulations, nonetheless, do assert two constitutionally based exceptions—sudden emergencies and protection of federal property.13 The PCA also does not apply where Congress has expressly authorized use of the military to execute the law. Congress has done so in three ways: by giving a branch of the armed forces civilian law enforcement authority (e.g., the Coast Guard), by addressing certain circumstances with more narrowly crafted legislation,14 and by establishing general rules for certain types of assistance. The military indirectly supports border security and immigration control efforts under general legislation that authorizes the armed forces to support federal, state, and local LEAs. Since the early 1980s, Congress has periodically authorized an expanded role for the military in providing support to LEAs. Basic authority for most DOD assistance was originally passed in 1981 and is contained in Chapter 18 of Title 10 of the U.S. Code—Military Support for Civilian Law Enforcement Agencies. Under Chapter 18 of Title 10, Congress authorizes DOD to share information (§371); loan equipment and facilities (§372); provide expert advice and training (§373); and maintain and operate equipment (§374). For federal LEAs, DOD personnel may be made available, under §374, to maintain and operate equipment in conjunction with counterterrorism operations (including the rendition of a suspected terrorist from a foreign country) or the enforcement of counterdrug laws, immigration laws, and customs requirements. For any civilian LEA, §374 allows DOD personnel to maintain and operate equipment for a variety of purposes, including aerial reconnaissance and the detection, monitoring, and communication of air and sea traffic, and of surface traffic outside the United States or within 25 miles of U.S. borders, if first detected outside the border. Congress placed several stipulations on Chapter 18 assistance, e.g., LEAs must reimburse DOD for the support it provides unless the support "is provided in the normal course of military training or operations" or if it "results in a benefit...substantially equivalent to that which would otherwise be obtained from military operations or training."15 Pursuant to §376, DOD can only provide such assistance if it does not adversely affect "the military preparedness of the United States." Congress incorporated posse comitatus restrictions into Chapter 18 activities in §375. In 1989, Congress began to expand the military's support role. For example, Congress directed DOD, to the maximum extent practicable, to conduct military training exercises in drug-interdiction areas, and made the DOD the lead federal agency for the detection and monitoring of aerial and maritime transit of illegal drugs into the United States.16 Congress later provided additional authorities for military support to LEAs specifically for counterdrug purposes in the National Defense Authorization Act for FY1991.17 Section 1004 authorized DOD to extend support in several areas to any federal, state, and local (and sometimes foreign) LEA requesting counterdrug assistance. This section has been extended regularly and is now in force through the end of FY2011.18 As amended, §1004 authorizes the military to: maintain, upgrade, and repair military equipment; transport federal, state, local, and foreign law enforcement personnel and equipment within or outside the U.S.; establish bases for operations or training; train law enforcement personnel in counterdrug activities; detect, monitor, and communicate movements of air, sea, and surface traffic outside the U.S., and within 25 miles of the border if the detection occurred outside the U.S.; construct roads, fences, and lighting along U.S. border; provide linguists and intelligence analysis services; conduct aerial and ground reconnaissance; and establish command, control, communication, and computer networks for improved integration of law enforcement, active military, and National Guard activities. Section 1004 incorporates the posse comitatus restrictions of Chapter 18.19 Unlike Chapter 18, however, this law does allow support which could affect military readiness in the short-term, provided the Secretary of Defense believes the support outweighs such short-term adverse effect.