The Posse Comitatus Act and Related Matters: The Use of the Military to Execute Civilian Law
Released: 2018-11-06T00:00:00

Summary:
The Constitution permits Congress to authorize the use of the militia "to execute the Laws of the Union, suppress Insurrections and repel Invasions." And it guarantees the states protection against invasion or usurpation of their "republican form of government," and, upon the request of the state legislature, against "domestic violence." These constitutional provisions are reflected in the Insurrection Acts, which have been invoked numerous times both before and after passage of the Posse Comitatus Act, 18 U.S.C. Section 1385, in 1878. Congress has also enacted a number of statutes that authorize the use of land and naval forces to execute their objective.
The Posse Comitatus Act outlaws the willful use of any part of the Army or Air Force to execute the law unless expressly authorized by the Constitution or an act of Congress. History supplies the grist for an argument that the Constitution prohibits military involvement in civilian affairs subject to only limited alterations by Congress or the President, but the courts do not appear to have ever accepted the argument unless violation of more explicit constitutional command could also be shown. The express statutory exceptions include the legislation that allows the President to use military force to suppress insurrection or to enforce federal authority, 10 U.S.C. Sections 251-255, and laws that permit the Department of Defense to provide federal, state and local police with information, equipment, and personnel, 10 U.S.C. §§ 271-284.
Case law indicates that "execution of the law" in violation of the Posse Comitatus Act occurs (a) when the Armed Forces perform tasks assigned to an organ of civil government, or (b) when the Armed Forces perform tasks assigned to them solely for purposes of civilian government. Questions concerning the act's application arise most often in the context of assistance to civilian police. At least in this context, the courts have held that, absent a recognized exception, the Posse Comitatus Act is violated when (1) civilian law enforcement officials make "direct active use" of military investigators; or (2) the use of the military "pervades the activities" of the civilian officials; or (3) the military is used so as to subject "citizens to the exercise of military power which was regulatory, prescriptive, or compulsory in nature." The act is not violated when the Armed Forces conduct activities for a military purpose.
The language of the act mentions only the Army and the Air Force, but it is applicable to the Navy and Marines by virtue of administrative action and commands of other laws. The law enforcement functions of the Coast Guard have been expressly authorized by act of Congress and consequently cannot be said to be contrary to the act. The act has been applied to the National Guard when it is in federal service, to civilian employees of the Armed Forces, and to off-duty military personnel. The act probably only applies within the geographical confines of the United States, but supplemental provisions of 10 U.S.C. §§ 271-284 appear to apply worldwide.
Finally, the act is a criminal statute under which there has been but a handful of known prosecutions. Although violations will on rare occasions result in the exclusion of evidence, the dismissal of criminal charges, or a civil cause of action, as a practical matter compliance is ordinarily the result of military self-restraint.
This report provides an historical analysis of the use of the Armed Forces to execute domestic law and of the Posse Comitatus Act, including their apparent theoretical and constitutional underpinnings. The report then outlines the current application of the act as well as its statutory exceptions, and reviews the consequences of its violation. This report appears in abridged form as CRS Report R42669, The Posse Comitatus Act and Related Matters: A Sketch.

paragraphs: Whoever, except in cases and under circumstances expressly authorized by the Constitution or Act of Congress, willfully uses any part of the Army or the Air Force as a posse comitatus or otherwise to execute the laws shall be fined under this title or imprisoned not more than two years, or both. 18 U.S.C. § 1385.
subsections: section_title: Introduction
paragraphs: Americans have a tradition, born in England and developed in the early years of our nation, that abhors military involvement in civilian affairs, at least under ordinary circumstances. It finds its most tangible expression in the 19 th century Posse Comitatus Act, 18 U.S.C. Section 1385, which forbids use of the Army and (as amended) the Air Force to execute civil law except where expressly authorized.
The exception documents a contrary component of the tradition. Congress has expressly approved the use of the Armed Forces in extraordinary circumstances or where federal manpower to enforce the law was seen as inadequate. Striking the balance between rule and exception has never been easy, but failure to do so has often proven unfortunate. If the rule is too unforgiving, a Shays's Rebellion may go unchecked. If exceptions are too generously granted, a Boston Massacre or Kent State tragedy may follow.
The terrorist attacks against the United States in September 2001 produced some calls for more generous exceptions to the rule. The USA PATRIOT Act broadened the permissible circumstances for the use of the military to assist law enforcement agencies in countering terrorism, but Congress also reaffirmed its determination to maintain the principle of the posse comitatus law. The perceived breakdown in civil law and order in Hurricane Katrina's wake evoked more calls to reevaluate the military's role in responding to disasters. The possibility of using military surveillance equipment and resources, including unmanned aerial vehicles (drones), to assist civilian law enforcement has raised some objections based on the military role. This report provides an historical analysis of the use of the Armed Forces to execute domestic law and of the Posse Comitatus Act, including their apparent theoretical and constitutional underpinnings. The report then outlines the current application of the Posse Comitatus Act as well as its statutory exceptions, and reviews the consequences of its violation.
section_title: Background
paragraphs: The Magna Carta provides the first recorded acknowledgment of the origins of the Anglo-American tradition against military involvement in civilian affairs with its declaration that "no free man shall be ... imprisoned ... or in any other way destroyed ... except by the legal judgment of his peers or by the law of the land." Subsequent legislation in the reign of Edward III explained that this precluded punishment by the King except "in due Manner ... or by Process made by Writ ... [or] by Course of the Law," or as later more simply stated, except "by due Process of the Law." Three hundred years after the passage of the Edwardian statutes, Lord Coke and other members of Parliament read these due process and law of the land requirements to include a broad prohibition against the use of martial law in peacetime, an interpretation they compelled King Charles I to acknowledge.
King Charles I, preparing for a military expedition in France, had quartered his troops in homes along the southern English coastline. Rioting resulted, and the participants, both military and civilian, were tried and punished by commissioners operating under the authority of martial law. Offended by this peacetime exercise of military judicial authority over civilians, Parliament sought and was granted the Petition of Right of 1628, which outlawed both quartering and martial law commissions.
When, in the following century, the British responded to colonial unrest by quartering troops in Boston, the colonists saw it as a breach of this fundamental promise of English law. Their circumstances, however, were not exactly identical to those surrounding the Petition of Right. First, the question arose in the British colonies rather than England itself. England had stationed troops in the colonies to protect them against the French and Indians and had opted for military governorships in other territories. Second, there was no military usurpation of judicial functions. The colonists remained subject to civil rather than military justice, and soldiers who employed more force than civilian law permitted were themselves subject to civilian justice as the trial of the soldiers involved in the Boston Massacre demonstrates.
On the other hand, the troops involved in the Boston Massacre were stationed in Massachusetts not for protection against a marauding invader as they had been in the French and Indian Wars, nor to accomplish the transition between civil governments within a conquered territory as they had been after the French lost Canada to the British as a consequence of those conflicts, but as an independent military force quartered among a disgruntled civilian population to police it. Public resentment of the use of the troops in such a manner sparked the incident, which led in turn to further heightened resentment.
In any event, the experience was sufficiently vexing that the Declaration of Independence listed among our grievances against Great Britain that the King had "kept among us, in times of peace, Standing Armies without the consent of our legislatures," had "affected to render the Military independent of and superior to the civil power," and had "quarter[ed] large bodies of armed troops among us ... protecting them, by a mock trial, from punishment for any murders which they should commit on the inhabitants of these States."
The Articles of Confederation for the newly established United States addressed the threat of military intrusion into civilian affairs by demanding that the Armed Forces assembled during peacetime be no more numerous than absolutely necessary for the common defense; by entrusting control to civil authorities within the states; and by a preference for the farmer in arms as a member of the militia over the standing professional army.
The Constitution continued these themes, albeit with greater authority vested in the federal government. It provided that a civilian (the President) should be the Commander in Chief of the Army and Navy of the United States, and civilian authorities (Congress) should be solely empowered to raise and support Armies, provide and maintain a Navy, and make rules for their government and regulation. The Bill of Rights limited the quartering of troops in private homes, and noted that "a well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed." The Constitution, on the other hand, explicitly permitted Congress to provide for calling out the militia to execute the laws, suppress insurrection, and repel invasion.
section_title: The Use of Federal Troops Prior to 1878
paragraphs: Notwithstanding the founders' aversion to the use of a standing army to control the civilian populace, the Constitution nowhere explicitly prohibits it, and Congress lost no time in authorizing the President to call out the militia for the purposes permitted under the Constitution. Despite the retention of most police powers by the several states, Congress quickly established a law enforcement capability in the federal government in order to effectuate its constitutional powers and provide a means to enforce the process of federal courts. This authority was vested through the President in federal marshals, who were empowered to call upon the posse comitatus to assist them, an authority similar to that enjoyed by the sheriff at common law, and which was understood to include the authority to call for military assistance.
Thus, the militia under federal control (and later the Armed Forces ) could operate either as an arm of the government or to support the federal marshal. These two roles of the military were similar in many respects, but, at least in theory, differed in one key aspect: troops serving as a posse comitatus remained subordinate to civil law enforcement authorities, while troops called up to suppress an insurrection or remove an obstruction to the execution of the laws supplanted civil authorities that had been rendered ineffective. In some cases, if the marshal feared he would be unable to control a disturbance even with the aid of a posse, or if local military commanders declined to give assistance, the marshal would try to persuade the President that an insurrection was underway. At other times, the President might order troops to quell what appeared to amount to an insurrection, yet limit the role of the Armed Forces to responding to the requests of the appropriate civil official, possibly dispensing with the need to issue the requisite proclamation under the Insurrection Act.
In addition, Congress has from time to time enacted statutes authorizing federal troops to enforce specific proscriptions, sometimes in aid of civil authorities and sometimes (apparently) in their stead, and Presidents have issued proclamations exhorting all federal officials, civilian or military, to assist in arresting a particular conspiracy or uprising. It is not always easy to ascertain which statutory authority (if any) forms the basis for sending in federal troops.
Presidents have relied upon the militia and Armed Forces with some frequency for riot control or when in extreme cases they felt it necessary to ensure the execution of federal law. The following sections provide an overview of the domestic employment of military forces and the statutes that govern such use.
subsections: section_title: The Insurrection Act and Other Statutes
paragraphs: Soon after Congress was first assembled under the Constitution, it authorized the President to call out the militia, initially to protect the frontier against "hostile incursions of the Indians," and subsequently in cases of invasion, insurrection, or obstruction of the laws. Shortly thereafter, and echoing Article I, Section 8, cl. 15 and Article IV, Section 4 of the Constitution, Congress enacted the Calling Forth Act, authorizing the President to call out the militia in case of invasion or, at the request of a state legislature (or its governor, if the legislature could not be convened) in case of an insurrection within a state. Congress also empowered the President to call forth the militia, for a period of 30 days:
whenever the laws of the United States shall be opposed, or the execution thereof obstructed, in any state, by combinations too powerful to be suppressed by the ordinary course of judicial proceedings, or by the powers vested in the marshals by this act, the same being notified to the President of the United States, by an associate justice or the district judge.
In any of these events, the President was first required to issue a proclamation commanding the "insurgents" to disperse. President Washington used this authority to put down the Whiskey Rebellion in western Pennsylvania. Resistance to an excise tax on distilled whiskey led to violence against tax collectors; indictments of those perpetrating the violence went unanswered, and farmers eventually rose in rebellion against all efforts to enforce the federal law. The governor, having declined to call out the state militia to control the violence, the federal courts were left to call on the federal government for assistance. When the rioters failed to disperse on the President's proclamation, some fifteen thousand militiamen from Pennsylvania and neighboring states quickly mobilized to restore the peace.
After the Calling Forth Act expired two years later, Congress reenacted virtually the same language, except that a court finding was no longer necessary, and the proclamation to disperse did not have to occur prior to calling up the militia. It appears that the revised Calling Forth Act was understood to cover the use of the militia as an aid to civilian power or, in rare cases, as a means of temporarily supplanting local civilian authority. 
Both provisions of the Calling Forth Act were extended in 1807 to allow for the employment of the Army and Navy in domestic circumstances where the militia could be employed. Even before this change, President John Adams had used regular federal troops to put down, more by intimidation rather than the actual use of force, the 1799 Fries Rebellion in eastern Pennsylvania. The cavalry arrested the instigator of the resistance, John Fries, along with other participants, and turned them over to civil authorities to be tried for treason. Those convicted were eventually pardoned.
subsections: section_title: Resistance to Taxes and Duties
paragraphs: As in the Whiskey and Fries Rebellions, resistance to the laws of the United States during the early years of the republic had mainly to do with citizens' objections to steadily increasing federal taxes, which were largely necessary to build up the military establishment, and other laws that tended to make themselves felt in citizens' pocketbooks. In 1808, President Jefferson called out federal troops to suppress opposition to the Embargo Act by groups of traders in Vermont whose livelihood depended on imports and exports with Canada. Although President Jefferson followed the contemporary practice of turning to states' governors to supply militia in support of revenue collectors, the state militia troops proved reluctant to enforce the law against their neighbors, so the President sent in a detachment of regular troops to restore order. Congress subsequently amended the Embargo Act specifically to authorize the use of troops to enforce the embargo. Resentment at the newly enacted authority to use federal military force to enforce ordinary laws in the absence of armed resistance led to a speedy demise of the embargo statute. 
In 1832, resistance to revenue laws again led to the prospect of using federal troops. Southerners objected to the system of protective tariffs that had been adopted in 1816 after the post-war resumption of trade threatened new domestic industries. Rather than gradually reducing the tariffs, as it had indicated was its intent, Congress steadily increased the tariff until by 1832 it became a policy fixture. Southerners believed that the money was raised unfairly at their expense and was expended mainly for the benefit of Northerners. The legislature of South Carolina voted to nullify the tariff and declared the state ready to meet force with force in the event the federal government sought to collect the tax. Congress passed a "Force Bill" to authorize the President to use the Army and Navy to collect duties, but at the same time reduced the duties. South Carolina rescinded its nullification ordinance, bringing the confrontation to an end without the use of force (although, as a final defiant gesture, it issued a new ordinance to nullify the Force Bill).
section_title: Neutrality Act Enforcement
paragraphs: The early U.S. desire to avoid foreign entanglements of the sort that kept Europe in arms during the founders' era manifested itself in a policy of neutrality which tended, at times, to conflict with the economic interests or political views of some part of the citizenry. Congress enacted a statute to prohibit the enlistment in or recruitment for foreign military service, the arming of foreign war vessels or privateers, and the dispatch of military expeditions against the territory of a state at peace with the United States. The statute also empowered the President to call upon the Armed Forces to detain or take possession of illicitly armed vessels and to prevent expeditions from departing U.S. territory. Even prior to its enactment, President Washington had called on state militias to deal with efforts of the French Ambassador to fit out privateers and military expeditions against British and Spanish interests. President Jefferson relied on this authority to counter Aaron Burr's conspiracy in 1806 as well as other schemes to liberate Spain's South American colonies. State militias employed for this purpose remained under the control of their respective governors.
In 1836, at the time of Texas's struggle for independence from Mexico, the Armed Forces were employed in an effort to prevent armed American sympathizers from crossing the border to join the fight in violation of the Neutrality Act of 1818, which expressly authorized the employment of the militia and Armed Forces in its enforcement. The next year, the Army was employed in a similar vein to quiet militant activity along the Canadian border. President Zachary Taylor issued a proclamation urging all officials, "civil and military," to halt a planned expedition to attack Cuba, which resulted in the Navy dispatching vessels to New Orleans to prevent the expedition from departing. To block American sympathizers from aiding Cuban separatists during the Ten Years' War and to halt Fenian expeditions against Canada, President Grant issued a proclamation in 1870 urging civil and military officers to take measures to prevent expeditions in violation of neutrality and to bring violators to justice. 
section_title: Requests from States for Military Aid
paragraphs: Section 2 of the Calling Forth Act, authorizing the President to employ military force when the state made a proper application for assistance, lay dormant until the 1830s, when violence between contending groups of Irish laborers on the Chesapeake and Ohio Canal led Maryland's legislature to request federal aid in 1834. President Jackson promptly endorsed the request to the Secretary of War and ordered "at least two companies of regulars" be sent to aid state civil authorities, without, however, issuing a proclamation to the laborers to disperse. The presence of federal troops helped to stabilize the situation without requiring any actual use of force.
A second request was occasioned in 1838, when both parties to the Pennsylvania state election claimed victory and set about to establish majority control of the state House. When public reaction turned violent, the governor called out the militia and requested aid from the local military commander, who denied the request. The governor then appealed to President Van Buren for federal assistance under the Domestic Violence Clause of the Constitution. Despite that clause's guarantee of protection, President Van Buren took the position that his duty was discretionary, and believing the domestic violence was not of a character that the "State authorities, civil and military ... have proved inadequate to suppress it," he declined to authorize assistance. In the meantime, however, the commanding general of the U.S. arsenal at Frankford brought men and ordnance in response to the governor's request. The "Buckshot War" ended without armed confrontation, but the commander was reprimanded by the War Department for acting without authorization.
A more serious state of affairs was reached in Rhode Island in 1842, where dissatisfaction with the government under the state's charter, still that granted by King Charles II in 1663, led to efforts to draft a new constitution. Two separate conventions were established, resulting in two separate sets of government officials claiming legitimate authority. The governor under the charter declared martial law and requested the President provide federal troops to stop the feared violence, but President Tyler declared he had no power to anticipate insurrections. Three subsequent similar requests were similarly denied. By the time the President had decided that intervention might be necessary to prevent the opposition army (led by contending Governor Thomas Dorr) from using force, the Secretary of War had determined that Dorr's men had dispersed, and the already-prepared proclamation would not be necessary. 
The "Dorr Rebellion" had ended without a clash of arms. It did, however, produce a seminal Supreme Court decision, Luther v. Borden . In Luther , among other things, the Court established that whether a state enjoys a republican form of government guaranteed by the Constitution was a political matter for Congress to decide. Moreover, the Court indicated that Congress having delegated to the President its prerogative to call forth the militia in cases of domestic violence, it is up to the President to determine the exigency of responding to a call from a state for military intervention to put down a claimed insurrection. In either case, the Court determined the judiciary has no role to play.
After the Civil War, labor disputes led to numerous requests for federal troops to suppress violence. In 1877, in response to strikes and related violence that erupted after railroads cut the pay of their workers by 10%, federal troops were requested by the governors of Pennsylvania, West Virginia, Maryland, Illinois, and Missouri, Indiana, Wisconsin, California, and Kentucky, with varying degrees of conformity to the requirements of the Insurrection Act, as interpreted by President Hayes. Although Ohio's governor did not request federal troops to quell strike-related violence in Toledo, Cincinnati, and other places, local officials appealed for assistance from nearby military commanders. No direct help was given, although supplies of arms from Rock Island Arsenal were made available to the state. It has been suggested that federal authority might have been asserted on the basis of the protection of a federal function (i.e., the delivery of the mail), but either due to an understanding that federal assistance to enforce state law was constitutionally unavailable without the request of the state government, or due to the lack of available federal troops, the President made no effort to do so.
Questions regarding the federal versus state control of troops arose during the 1877 riots. In West Virginia and Maryland, federal troops were placed under the command of the governors to be employed alongside state troops. In Indiana, where the governor's request was initially turned down for lack of compliance under the Constitution and Insurrection Act, federal troops were to be furnished on the request of the federal marshal as a posse comitatus and were not turned over to the governor. When disorder spread to Pennsylvania, federal troops were initially sent in to protect federal property, the governor's first request for assistance having apparently been deemed deficient. After the deficiencies were corrected and a proclamation was issued, the general officer in charge of federal troops requested clarification as to the disposition of federal troops and espoused the doctrine that whenever a state government asks for assistance under the Insurrection Act, federal military power should supplant local civil authority:
When the governor of a State has declared his inability to suppress an insurrection and has called upon the President of the United States under the Constitution to do so, that from that time commences a state not of peace but of war, and that although civil local authority still exists, yet the only outcome is to resort to force through the Federal military authorities, and that can only be through a subordination of the State authorities for the time being and until lawful order is restored; otherwise there can be no complete exercise of power in a military way within the limits of the State by the Federal officers. 
The doctrine appears to have gained the approval of President Hayes, at least insofar as it had to do with command of state troops, although a telegram advising the commander to in effect federalize state troops arrived too late to be carried into effect. The proposed equation of insurrection to war calling for the substitution of military force for ordinary methods of law enforcement seems to have found its way into later War Department manuals regarding the military role in civil disturbances.
section_title: Trouble in the Western States and Territories
paragraphs: U.S. troops were sent to deal with disputes in western territories and new states on several occasions. In California, the failure of the governor to request assistance under the Insurrection Act led to a denial of military assistance. The California Gold Rush was marked by a heightened tendency toward lawlessness, which was for a time brought under relative control by vigilantes. The self-appointed Vigilance Committee of San Francisco, which had been allowed to operate separately from federal and local law enforcement authorities, refused to surrender a prisoner to the federal court under a writ of habeas corpus. The governor called out the militia to put down the insurrection, and, having received a less than enthusiastic response, requested assistance from the Army, and when that was refused, from the President. The Attorney General advised the President that the situation was not sufficiently dire to require federal intervention, and noted that during the month of turmoil said to require armed intervention, no effort had been made to convene the legislature. When the Vigilante Committee took another prisoner, a judge of the California Supreme Court, the state governor again requested assistance from the military, this time from the commander of a ship in the harbor. Again, the request was turned down. The senior naval commander in San Francisco, stressing the constitutional requirements for requesting aid from the federal government to put down domestic violence, instructed the ship's captain that there was to be no interference in the domestic troubles of the state.
The territory of Utah was the site of considerable resistance to federal law after it was established in 1850, and Brigham Young, the head of the Church of Jesus Christ of Latter-day Saints, appointed its governor. Most white inhabitants of Utah were also members of the Church and tended to regard laws not emanating from the governor to be invalid, eventually compelling nearly all federal officials to leave the territory for their own safety. In 1857, the President appointed a new governor, and federal Armed Forces were sent in to ensure a peaceful transfer of power. Governor Young responded by declaring martial law and forbidding any Armed Forces from entering the territory. It was not until April 1858 that President Buchanan issued a proclamation offering amnesty to those who would obey the law and promising to prosecute those who did not. The proclamation was not styled as an order to disperse, and troops were instructed to act in aid of the execution of civil power.
section_title: Slavery, the Civil War, and Reconstruction
paragraphs: In 1831, federal troops were sent out on several occasions to respond to reports of slave insurrections, initially in New Orleans and later in Virginia, Maryland, Delaware, and the Carolinas. These actions appear to have been undertaken by the local military commandants in response to requests from local officials, and do not appear to have been justified by any statute or presidential proclamation.
During troubles related to the slavery issue in Kansas in 1856, President Pierce issued a proclamation commanding persons involved in unlawful combinations to disperse. In the following months, the new governor sent frequent requests to the commandants at Ft. Leavenworth and Ft. Riley for troops to disband a territorial militia that had formed in Lawrence. When Kansas's pending entry into the Union in 1858 again brought tensions to a head, the governor called upon the commander of U.S. troops for troops to act "as a posse comitatus in aid of the civil authorities." There does not appear to have been another proclamation under the Insurrection Act, and since only the federal marshal and his deputies were empowered to request the assistance of the military as a posse comitatus, there was no statutory basis for this action. Rather, it appears to have been an exercise of the newly emerging theory known as the Cushing Doctrine, explained below, under which members of the Armed Forces could act as a posse comitatus to enforce the law without invoking the Insurrection Act or other law that permitted the use of the Armed Forces. 
At the dawn of the secessionist movement that led to the Civil War, President Buchanan declined to send troops into seceding states, apparently based on his perception that any troops dispatched to execute the laws of the Union would necessarily be subordinate to civil authorities. He informed Congress that because federal law enforcement and judicial machinery in those areas had already been demolished, his duty to execute the law could not be accomplished even with the aid of military troops. On coming into office, President Lincoln took a very different view, at times using federal military power without subordination to civil authority even in loyal Union states. Congress also enacted a new provision to replace § 2 of the Calling Forth Act, adding "rebellions" to instances for which the use of the Armed Forces was envisioned and to change the standard from a situation in which a combination or obstruction to law enforcement was "too powerful to be suppressed by the ordinary course of judicial proceedings" to one in which the unlawful obstruction or assemblage "make[s] it impracticable to enforce the laws ... by the ordinary course of judicial proceedings." 
The successful suppression of the rebellion did not put an end to violence in the South. The Reconstruction period after the Civil War was characterized by constant political turbulence in the South. Efforts to establish new governments in former Confederate states were particularly contentious during the decade following the Civil War, and Presidents received more requests for military aid from state governors during these years than all previous decades combined, sometimes receiving simultaneous requests from two rival governors claiming legitimacy in the same state after an election.
Resistance to efforts to achieve equal status for newly freed slaves led Congress to pass the Civil Rights Act of 1871 (also called the "Ku Klux Klan Act"), which among other things added a new insurrection provision permitting the President to employ the land and naval forces to enforce civil rights. This authority was used immediately after enactment when President Grant issued a proclamation calling attention to the new law and declaring himself ready to invoke it if necessary. This was followed several months later by a proclamation under the new act commanding conspirators in nine counties in South Carolina to disperse within five days and turn in their firearms, ammunition, and disguises to the local marshals or military officers, and shortly thereafter by a proclamation suspending habeas corpus, as permitted under Section 4 of the act. Hundreds of suspected Klansmen were arrested over the following months and tried in federal court.
section_title: Use of Military Forces as a Posse Comitatus
paragraphs: Even though Congress had since 1792 empowered the President to call out the state militia to overcome obstructions to law enforcement and it had also provided authority in a number of statutes for the President to employ the land and naval forces for certain law enforcement purposes, it appears to have been understood that federal law enforcement officials could themselves call on local military commanders for assistance without involving the President. Congress had vested the federal equivalent of the sheriff, the federal marshal, with the power to call forth the posse comitatus in performance of his duties. The federal marshals and their deputies were thus implicitly empowered to compel the assistance of members of the Armed Forces when force became necessary to execute the process of federal courts, but the military units serving on a posse were to remain subordinate to the marshal and could not initiate legal proceedings.
In some cases when it passed a particular statute, Congress specifically authorized recourse to the posse comitatus for its enforcement. The Fugitive Slave Act was such a law, and its use led to the crystallization of the government's doctrine regarding the use of the military in the role of a posse. Under that act, owners whose slaves had escaped to another state were entitled to an arrest warrant for the slaves and to have the warrant executed by the federal marshals. The marshals in turn might "summon and call to their aid the bystanders, or posse comitatus of the proper county ... [and] all good citizens [were] commanded to aid and assist in the prompt and efficient execution of this law, whenever their services may be required, as aforesaid, for that purpose." The act did not specifically authorize the use of the military or militia in its execution, but when particularly fierce opposition arose in Boston in 1851, the President issued a proclamation requiring "all officers and persons, civil and military to aid and assist by all means in their power in quelling [such] combinations.... " The Secretary of War sent orders to Army units to be ready to respond to the call of a marshal or deputy, or the certification of a federal judge stating that military force would likely be necessary. Troops in Boston Harbor were made ready to intervene in the event of a riot, but such intervention was unnecessary. 
When asked by the Senate whether sufficient authority for vigorous enforcement of the Fugitive Slave Act was available, President Fillmore advanced the doctrine that his use of the Army and Navy to enforce federal law was an inherent power, suggesting that it ought not be construed as restricted by the Insurrection Act's requirements, in particular that of issuing a proclamation to disperse. He also made the argument that all citizens, whether enrolled in any military service or not, may be summoned as a posse comitatus, while conceding doubt as to whether an organized military force acting under military command might be employed in such a manner. The Senate Judiciary Committee declared that it saw no reason to consider military members exempt from duty to serve as a posse comitatus, whether as individuals or organized under their ordinary command structure.
In June of 1851, a federal marshal in Chicago arrested a fugitive slave on a warrant issued under the act. He called for the assistance of members of the police force and of the state militia to prevent abolitionists from rescuing the prisoner before he could be returned to his owner. The marshal subsequently filed a claim with the Department of the Treasury for reimbursement of the funds he had paid the members of the police force and the militia who responded to his call. Attorney General Caleb Cushing was asked whether the United States was obligated to honor the claim. While this question remained pending, another incident in Boston arose in response to the arrest of fugitive slave Anthony Burns in 1854. Two batteries of artillery and a detachment of federal troops were sent into the city while the governor also called up the local militia, but when additional forces were requested, military commanders considered further authorization from Washington to be necessary before complying with the requests.
The Attorney General took the opportunity, ostensibly in response to the earlier request, to announce a new doctrine regarding the employment of the Armed Forces. Cushing's response went well beyond the question of whether the "bystanders" contemplated by the Fugitive Slave Act might include members of a state militia when not in federal service, and announced a broader principle—members of the military by virtue of their duties as citizens were part of the posse comitatus. Apparently adopting the views expressed earlier by the Senate Judiciary Committee in reaction to the previous Administration's views on the matter, Cushing declared:
The posse comitatus comprises every person in the district or county above the age of fifteen years, whatever may be their occupation, whether civilians or not; and including the military of all denominations, militia, soldiers, marines, all of whom are alike bound to obey the commands of the sheriff or marshal. The fact that they are organized as military bodies, under the immediate command of their own officers, does not in any wise affect their legal character. They are still the posse comitatus. (xxi Parl. Hist., p.672, 688, per Lord Mansfield).
Two years later, Cushing's opinion supplied the justification for the use of federal troops at the call of civil law enforcement authorities in what some saw as partisan involvement in the conflict between pro- and anti-slavery forces in Kansas. Congress reacted with a rider to an Army appropriations bill forbidding the use of any "part of the military forces of the United States to enforce territorial law in Kansas." After some discussion of whether the amendment was germane, it was defeated. 
section_title: Passage of the Posse Comitatus Act
paragraphs: Following the Civil War, the use of federal troops to execute the laws, particularly in the states that had been part of the Confederacy, continued even after all other political restrictions had been lifted. By 1877, there was evidence that Republican state governments in more than one southern state owed their continued political existence to the presence of the military and that the activities of federal troops may have influenced the outcome of the Hayes-Tilden presidential election.
The House of Representatives, controlled by a Democratic majority, passed an Army appropriation bill which expressly prohibited use of the Army to shore up Republican state governments in the South, or more precisely, to shore up either side of the political dispute in Louisiana or anywhere else. The Senate, controlled by a Republican majority, refused to accept the provision. No compromise could be reached, and the session ended without passage of an Army appropriation bill. Money to pay the Army was subsequently appropriated in a special session, without reference to restrictions on use of the Army. But when the issue of Army appropriations next arose, the House included a posse comitatus section. The Senate accepted the House version with minor amendments.
At least one contemporary military jurist viewed the new law as having less than a momentous impact on the relationship between civil and military authorities. Colonel William Winthrop opined that, the occasion for its enactment having passed, the act remained "a mere impediment to the constitutional exercise of the executive power of the nation." While federal marshals could no longer avail themselves of military assistance to arrest individuals charged with offenses against the United States, he stressed that wherever a combination existed to resist the enforcement of the laws, the President always could invoke the Insurrection Act. He further made note of the already sizable list of exceptions to the prohibition.
Others have viewed the act as having a deleterious effect on the nation's commitment to civilian law enforcement. While soldiers serving on a posse remained subordinate to civilian rules and law enforcement officers, troops called out under the Insurrection Act came to be viewed as an independent military force enforcing something like martial law, if not engaging in all-out war. Today, however, the act is widely regarded as the embodiment of the American tradition of anti-militarism.
Despite early efforts on the part of the executive branch to get the provision repealed or amended, the Posse Comitatus Act has remained essentially unchanged since its passage. Congress has, however, authorized a substantial number of exceptions and has buttressed the act with an additional proscription against use of the Armed Forces to make arrests or conduct searches and seizures.
section_title: Constitutional Considerations
paragraphs: The Posse Comitatus Act raises at least three constitutional questions: (1) To what extent does the Posse Comitatus Act track constitutional requirements, beyond the power of the President or Congress to adjust or ignore? (2) To what extent do the powers which the Constitution vests in the President limit the power of Congress to enact the Posse Comitatus Act or any other provision restricting the President's discretion to involve the Armed Forces in civilian affairs? (3) What specifically are the military law enforcement activities "expressly authorized in the Constitution" for purposes of the act?
subsections: section_title: Constitutional Origins
paragraphs: Lord Coke and his colleagues, in crafting the Petition of Right of 1628, found within that chapter of the Magna Carta and subsequent explanatory statutes that are the antecedents of our constitutional due process clauses a prohibition against martial law. In times of peace, this proscription would not abide either the quartering of troops among civilians or any form of martial law, be it imposed by tribunal or more summarily dispatched by soldiers controlling or punishing civilians.
The Declaration of Independence lists the imposition of martial law upon us among those affronts to fundamental liberties that irrevocably ruptured our political ties to Great Britain.
Finally, it is possible to see the protrusions of a larger, submerged constitutional principle which bars the use of the Armed Forces to solve civilian inconveniences in the Second, Third, and Fifth Amendments, with their promises of a civilian militia, freedom from the quartering of troops among us, and the benefits of due process.
This view is not without judicial support. The courts have demonstrated a rather long-standing reluctance to recognize the authority of military tribunals over civilians. And members of the Supreme Court seemed to acknowledge possible components of a larger principle in both Youngstown Sheet and Tube Co. v. Sawyer and Laird v. Tatum .
But if a larger anti-martial law principle lies beneath constitutional sands, visible only in these amendments and the spirit of the Posse Comitatus Act, it has remained remarkably dormant. Those regions from which it might have been expected to emerge have been characterized most by inactivity. The boundaries of the Third Amendment are virtually uncharted. Until recently, the outreaches of the militia-related Second Amendment appeared only slightly more visible. Even in the inviting context of the Posse Comitatus Act, the courts have generally avoided excursions into areas of its possible constitutional underpinnings.
On the other hand, the Constitution appears to recognize that military force might occasionally be called for in handling domestic affairs. It permits Congress to authorize the use of the militia "to execute the Laws of the Union, suppress Insurrections and repel Invasions." And it guarantees the states protection against invasion or usurpation of their "republican form of government," and, upon the request of the state legislature, against "domestic violence." While states are prohibited from keeping their own standing armies, they retain some control over their militias, subject to any constraints Congress may constitutionally impose, including the authority to call forth those forces to suppress insurrections or quell civil disturbances. The Constitution neither authorizes nor proscribes martial law (which is said to exist when civil authority is supplanted by military rule due to war or similar emergency), but it has been proclaimed on rare occasions. Lesser forms of military involvement in law enforcement have not been commonplace, but have not been particularly rare during the history of the republic.
Without more judicial guidance, it would appear that traditional reservations about military involvement in the execution of civilian law can only clearly be said to rise to the level of constitutional imperative when they take a form that offends some more explicit constitutional prohibition or guarantee such as the right to jury trial, grand jury indictment, or freedom from unreasonable searches and seizures. Consequently, beyond those specific constitutional provisions, Congress's constitutional authority to enact and adjust the provisions of the Posse Comitatus Act is largely a matter of the coordination of congressional and presidential powers.
section_title: Presidential vs. Congressional Powers
paragraphs: The case of conflicting congressional and presidential powers is easily stated if not easily resolved. On one hand, the Constitution requires the President to take care to see that the laws are faithfully executed, and designates him as Chief Executive and Commander in Chief of the Armed Forces. In this dual capacity, the presidency is the repository of both extensive responsibilities and broad prerogatives, not the least of which flow from Article IV, Section 4 of the Constitution, which guarantees the states a republican form of government and protection against invasion and domestic violence.
The Supreme Court has made it clear that the President is not dependent upon express constitutional or statutory authorization for the exercise of his powers. Thus, he may meet an emergency by appointing a marshal to protect a threatened Supreme Court Justice, although no statute expressly authorized appointment for such purposes. He must resist invasion by an enemy with force though Congress has yet to declare war. And when an emergency arises threatening the freedom of interstate commerce, transportation of the mails, or some other responsibility entrusted to the federal government, he may call upon "the army of the Nation, and all its militia ... to brush away the obstructions."
Some commentators feel that this implied or incidental constitutional authority to use the Armed Forces not only exists in the absence of congressional direction, but is immune from congressional direction or limitation.
On the other hand, Congress shares constitutional power over the laws and Armed Forces with the President. The Constitution gives Congress the power to make the laws whose faithful execution the President must take care to observe and which carry into execution Congress's own powers and those of the President. It likewise vests Congress with the power to establish, maintain, and regulate the Armed Forces; and with the power to describe the circumstances under which the militia may be called into federal service.
The Supreme Court has shed some light on the coordination of presidential and congressional powers concerning use of the military to enforce civilian law. The Court has pointed out that the President's power under the Guarantee Clause of Article IV, Section 4, which guarantees the states protection against domestic violence, is only provisionally effective until such time as Congress acts. And the President may not always use the Armed Forces to meet a domestic emergency when Congress has previously resisted an invitation to sanction their employment. Finally, even when Congress has disclaimed any intent to limit the exercise of the President's constitutional powers, the President's implied and incidental powers will not always trump conflicting, constitutionally grounded claims. 
section_title: Constitutional Exceptions
paragraphs: The Posse Comitatus Act does not apply "in cases and under circumstances expressly authorized by the Constitution." It has been said that the Constitution contains no provision expressly authorizing the use of the military to execute the law in such a way, and that this reference to constitutional exceptions was included as part of a face-saving compromise that consequently should be ignored.
When the phrase was added originally, those who opposed the Posse Comitatus Act believed that the Constitution vested implied and/or inherent powers upon the President to use the Armed Forces to execute the laws; those who urged its passage believed the President possessed no such powers. As initially passed by the House, the bill contained no constitutional exception. The Senate version contained an exception for instances authorized by the Constitution whether expressed or otherwise. The managers of each house described the compromise reached at conference and subsequently enacted as upholding the position of their respective bodies on the issue. While the House manager believed that retention of the word "expressly" was important to prevent the use of the Army wherever implied authority could be inferred, the Senate manager suggested that the term could safely be kept in without affecting the President's ability to act as required by the Constitution.
Early commentaries suggest that the word "expressly" must be ignored, for otherwise in their view the Posse Comitatus Act is a constitutionally impermissible effort to limit the implied or inherent powers of the President. The regulations covering the use of the Armed Forces during civil disturbances do not go quite that far, but they do assert two constitutionally based exceptions—sudden emergencies and protection of federal property.
The question of whether the constitutional exception contained in the Posse Comitatus Act includes instances where the President is acting under implied or inherent constitutional powers or whether it was merely a face-saving device is a question that may turn on whether Congress may constitutionally restrict the President's powers, if any, in the area—a question the courts have yet to answer.
section_title: When the Posse Comitatus Act Does Not Apply
paragraphs: In addition to any express constitutional exceptions, the use of the Armed Forces to execute federal law does not violate the Posse Comitatus Act when (1) an act of Congress expressly authorizes use of part of the Army or Air Force as a posse comitatus or otherwise to execute the law; (2) the activity in question does not involve use of part of the Armed Forces covered by the proscription; or (3) the activity in question does not constitute "execution of the law."
subsections: section_title: Statutory Exceptions
subsections: section_title: Generally
paragraphs: The Posse Comitatus Act does not apply where Congress has expressly authorized use of the military to execute the law. Congress has done so in three ways: (1) by giving a branch of the Armed Forces civilian law enforcement authority; (2) by establishing general rules for certain types of assistance; and (3) by addressing individual cases and circumstances with more narrowly crafted legislation. Thus it has vested the Coast Guard, a branch of the Armed Forces, with broad law enforcement responsibilities. Second, over time it has enacted a fairly extensive array of particularized statutes, like those authorizing the President to call out the Armed Forces in times of insurrection and domestic violence. Finally, it has passed general legislation permitting the Armed Forces to share information and equipment with civilian law enforcement agencies, subject to restrictions on engaging in direct and active law enforcement.
How explicit must a statutory exception be? If one believes the word "expressly" should be ignored with respect to the constitutionally based exception, consistency might suggest no more is required than that Congress authorize a thing to be done. To those so inclined, the position is further fortified when the statute authorizes executive branch action in circumstances where the President's faithful execution responsibility, coupled with the Administrative Housekeeping Statute, can be called into play. In this rarely espoused view, if an agency has statutory authority to perform a task, the military may be asked to help.
Others maintain that statutes which authorize assistance from federal agencies and departments generally in order to accomplish a particular task qualify as exceptions even if they do not mention the Department of Defense or any part of the military establishment by name. On the one hand, such legislation has ordinarily come into being after the Posse Comitatus Act and thus would ordinarily be thought to amend any conflicting earlier law. On the other hand, the use of military force in civilian affairs is such an extraordinary thing that perhaps it ought not be presumed, but rather found only where Congress has so stated in hoc verba.
The final and more commonly accepted proposition is that the phrase "in cases and under circumstances expressly authorized by ... Act of Congress" demands that the statutory exception specifically refer to some form of military assistance. 
section_title: The Insurrection Acts
paragraphs: The clearest statutory exceptions to the Posse Comitatus Act are found in the Insurrection Acts, described above, in which Congress has delegated authority to the President to call forth the military during an insurrection or civil disturbance. The modern version has changed little from the original enactments, and is now found in Chapter 13 of Title 10, U.S. Code. The three main authorities differ according to which constitutional provision they are meant to implement, but the provisions have often been used together or without specifying which part of Chapter 13 of Title 10, U.S. Code, provided the authority. In any case where the President considers it necessary to invoke the authority to use the militia or Armed Forces under these provisions, he is required by 10 U.S.C. Section 254 to issue a proclamation immediately ordering "insurgents to disperse and retire peaceably to their abodes within a limited time." 
The following sections describe the modern authorities and how they have been invoked since the passage of the Posse Comitatus Act, including some instances where a separate authority may have been used for similar purposes.
subsections: section_title: At the Request of a State
paragraphs: Section 251 of Title 10 (previously section 331 of Title 10) authorizes the President to use the military to suppress an insurrection at the request of a state legislature, or its governor, in the event the legislature cannot be convened. It is meant to fulfill the federal government's responsibility to protect states in the event of "domestic violence" (although the term "insurrection" is arguably much narrower than the phrase "domestic violence" in the Constitution). The first request by a governor for troops after enactment of the Posse Comitatus Act appears to have occurred in 1879, when the governor of Nebraska requested a company of troops to help protect a local court where the trial of a prominent outlaw was taking place, which had occasioned concern that the courthouse would be the scene of a rescue attempt by the portion of the band of outlaws still at large. This request was denied, however, as it was framed as a request to use the troops as a posse comitatus, which, according to the Secretary of War, had become unlawful following enactment of the Posse Comitatus Act, although if the situation were to become more dire, the governor could request aid from the President in the form of troops under military command. 
Another proclamation was issued under this provision in 1892 due to a miners' strike in Coeur d'Alene, ID. In 1899, President McKinley deployed 500 troops to Coeur D'Alene, ID, at the governor's request, to keep a conflict between union miners and mine owners under control, but did not issue a proclamation required by statute. Although by this time General Hancock's doctrine regarding the relationship between federal and state troops had gained acceptance, state officials directed operations there. When the governor of Colorado requested federal aid to assist state militia to cope with a coal miners' strike, Secretary of War Elihu Root informed the governor that any troops furnished pursuant to the relevant provision of the insurrection statutes would not be at the disposal of the governor, but would remain under the direction of the President.
During the early part of the 20 th century, Presidents generally insisted that governors comply with the requirements of the Insurrection Act and the Constitution in formulating requests for the assistance of the Army. After the governor of Nevada requested troops in 1907 to put down violence by a miners' union that was forcibly removing non-union workers from the area, nine companies of infantry were sent there, but told not to act until a proclamation was issued. The mere presence of troops having quieted the unruly element, no proclamation was issued. President Roosevelt chastised the governor for having requested federal troops without endeavoring to convene the legislature as required under the Constitution and Insurrection Act. In 1914, a miner's strike at Ludlow, Colorado, led the governor there to request federal troops, which President Wilson granted. 
In 1917, after virtually the entire National Guard was called into federal service for the war in Europe, the Secretary of War instituted a "Direct Access Policy" to permit local and state officials to make direct requests for the assistance of federal troops to reduce the burden on states. Between 1919 and 1920, federal troops were employed to assist in putting down labor disputes and other minor disturbances 29 times, all without the issuance of a presidential proclamation. Troops were deployed from the lumber mills of the Northwest to the copper mines in Arizona and New Mexico, and from the coal mines in Appalachia to the oil fields in Texas and Louisiana, justified on the need to keep up production for the war and replace absent state militia. Federal troops also intervened to keep the peace in several cities afflicted by racial quarrels. The policy was revoked in 1921 due to the perception that troops were being misused, and President Harding issued the requisite proclamation in order to send troops to quell a dispute involving West Virginia coal miners. The governor directed state police forces to act under the direction of the U.S. military commander.
At the request of the Commissioners of the District of Columbia, President Hoover used federal troops in 1932 to oust the Bonus Marchers from federal property in Washington, DC, but did not issue a proclamation. President Roosevelt turned down several requests during the 1930s to provide federal troops for strike duty, but directed the Secretary of War in 1941 to seize and operate an aviation plant where a strike threatened wartime fighter plane production. Although the Attorney General likened the situation to an insurrection, the President's order did not make reference to the insurrection statutes, nor was it accompanied by a proclamation to disperse. When faced with losing their deferred status under the draft, the workers promptly returned to the plant and resumed production under military supervision. Other labor disturbances were similarly addressed by having the Army or Navy seize and manage plants or railroads deemed necessary for the war effort, but these occurred under separate authorities.
During the Second World War, racial strife began to contribute once again to civil disturbances, although federal troops were only called in twice. At the request of the Michigan governor, President Roosevelt issued a proclamation and sent federal troops to Detroit to restore order during a race riot there. Troops were also sent to Philadelphia in 1944 to seize and operate the transportation system after white workers went on strike to protest the employment of some black workers as operators. This, however, was done pursuant to a 1916 statute that empowered the President, during time of war, to order the Secretary of War to take over the possession and operation of transportation systems as required for war efforts.
A race riot in Detroit led the Michigan governor to request troops in 1967, which President Johnson provided. Widespread violence in cities across the country following the assassination of Martin Luther King put the military establishment on alert for possible implementation of the government's plan for civil disturbances, Garden Plot. In the end, only the mayor of Washington, DC, and the governors of Illinois and Maryland requested assistance under the insurrection statutes. President Lyndon Johnson issued proclamations in April, 1968 ordering rioters to disperse in Washington, DC, Chicago, and Baltimore. Each proclamation mentioned both the request for assistance and the need to enforce federal law, citing the entire chapter on insurrections in Title 10 among relevant authorities. Regular troops and federalized National Guard were deployed to these cities. 
In 1989, reports of widespread looting on the island of St. Croix in the wake of Hurricane Hugo led President George H. W. Bush to issue a proclamation and send troops to the Virgin Islands, as the territorial governor requested federal intervention. The proclamation cited the need to enforce federal law and protect public property, without expressly mentioning the governor's request. Eleven hundred troops (mostly military police) and 80 federal investigators were sent to St. Croix to restore order and investigate reports of looting.
The most recent invocation of 10 U.S.C. § 251 (then codified at 10 U.S.C. § 331) occurred in 1992, when the acquittal of police officers on charges of beating motorist Rodney King sparked rioting in Los Angeles. The California National Guard, already on the scene but unable to control the violence, was federalized, which may have hampered its efforts due to a misunderstanding that the Guard troops under federal control could no longer carry out law enforcement operations due to the Posse Comitatus Act.
section_title: To Enforce Federal Law
paragraphs: Section 252 of Title 10 (previously section 332 of Title 10) delegates Congress's power under the Constitution to call forth the militia to the President, authorizing him to determine that "unlawful obstructions, combinations, or assemblages, or rebellion against the authority of the United States make it impracticable to enforce the laws of the United States" and to use the Armed Forces as he considers necessary to enforce the law or to suppress the rebellion. Its first application after the enactment of the Posse Comitatus Act involved an appeal by the governor of the Territory of New Mexico in 1878 for federal military assistance in putting an end to the anarchy that characterized the territory due to the operation of bands of robbers who were besieging mail coaches and terrorizing the local populace. After the proclamation to disperse was issued, military forces restored relative order, after which civil authorities reportedly came to depend on U.S. troops for law enforcement to such an extent that they essentially abandoned their own efforts to enforce the law. When the governor complained about the lack of military assistance for arresting lawbreakers, the local commanding general replied that his troops could not be used to make ordinary arrests in situations that did not amount to an insurrection or reach a level of lawlessness that would extend beyond the capacity of the usual civil machinery to handle. This interpretation of the new posse comitatus restriction was adopted by the War Department. The Secretary of War later blamed the Posse Comitatus Act in part for the fact that lawlessness and riots in the territory had reached such a level that military intervention was required. 
"Indian outrages" in Arizona led to another proclamation under the Insurrection Act, not at the request of the territorial governor but as a response to news that the governor was proposing to arm citizens to go after Apaches suspected of murder, which would oblige the military to take action to protect the reservation. President Arthur initially requested legislative relief from the Posse Comitatus Act due to his view that its prohibition inhibited an effective military response. Congress declined to repeal the prohibition, however, with the Senate Judiciary Committee pointing out that the Posse Comitatus Act was meant to curb the practice of local marshals and their subordinates employing the Armed Forces to assist them in enforcing the law, but not to prevent the President from himself using any part of the Army under a military chain of command. 
Federal troops were called to Chicago in July 1894 to quell riots accompanying the railroad strikes. President Grover Cleveland did not issue a proclamation for rioters to disperse until several days after violence had begun, after learning that troops had been compelled to fire on a mob in the nearby town of Hammond, IL. Another proclamation was issued the next day to remove further obstructions to the mail and execution of U.S. law occasioned by the strike as it spread westward. The governors of the afflicted states did not call for federal assistance; in fact, the governor of Illinois opposed intervention. Rather, the federal marshals and U.S. attorneys notified the Attorney General, who presented the requests to the President. It appears that obtaining civilian deputies to assist marshals against the strikers was made difficult due to the fact that popular sympathies were with the strikers, leading the civilian authorities to prefer shifting the responsibility to the Army. Federal troops were also used to recapture trains stolen by various "industrial armies" of disaffected miners and laborers. 
In 1885, resistance in Utah to the "Edmunds law" for the suppression of polygamy caused the governor of that territory to seek federal assistance, which was granted. Animosity toward Chinese railroad laborers and miners led to major disturbances and to calls for federal troops in a number of western states and territories in 1885-1886. Proclamations were issued for the state of Washington, but federal troops sent there met with no resistance. Federal troops were employed in Montana in 1897 to protect a prisoner charged with murder from a potential mob lynching, but this was done on the order of the local commander under "emergency authority," without a presidential proclamation. 
A proclamation was issued in 1914 to employ troops to suppress a riot in Arkansas to support the courts and protect government property. 
A large task force of regular troops, National Guard, federal marshals, and other police was assembled to protect the Pentagon during the 1967 anti-war demonstration known as the March on the Pentagon. In connection with this effort, the Army authorized a widespread covert intelligence operation to infiltrate protest groups who were planning to march, and radio communications were also monitored. Section 332 (now codified at 10 U.S.C. § 252) was considered in order to provide the legal justification, but rejected because violence was merely projected and a proclamation was thought to be too difficult to frame under such circumstances. In the end, authorities decided to rely on a non-statutory basis regarded as an implicit sovereign right to protect government property, although section 332 was held in reserve in case the level of violence called for federalizing the National Guard. There were a few clashes between troops and protesters, but the violence did not reach the threshold for invoking section 332.
The National Guard was called into service during a postal strike in 1970 to "execute the laws of the United States as they relate to the Post Office Department." The cited authority for this action was the Economy Act of 1932, which led to some criticism because that statute does not provide for the use of the Army. 
In 1973, the Army became involved in a federal law enforcement operation to quell a civil disturbance on the Pine Ridge Reservation in South Dakota after some 200 members of the American Indian Movement seized and occupied the village of Wounded Knee to demonstrate their grievances. The Attorney General advised President Nixon to send federal troops to the area, presumably under the authority of 10 U.S.C. § 332 (now § 252), but military advisors counseled against the idea. Instead, some 350 federal officers were sent to the scene, including a paramilitary group from the U.S. Marshals Service. Nevertheless, the 82d Airborne Division was tasked to provide a 1,000-man contingency force as well as some observers, and regional National Guard units provided surveillance aircraft and other equipment. The troops from the 82d Airborne were not deployed, but some questioned whether military aid supplied to civilian law enforcement was permissible under the Posse Comitatus Act, leading to litigation and eventually legislation to authorize some types of military support to civil authorities. (See below " Support to Law Enforcement .")
In 1987, President Reagan issued a proclamation to order rioting prisoners in the federal penitentiary in Atlanta, Georgia, to disperse. He authorized the Secretary of Defense to call up National Guard units or members to suppress the violence, specifying that the law enforcement policies determined by the Attorney General were to be followed. Local authorities were able to negotiate the release of hostages the prisoners had taken and bring an end to the trouble before troops arrived.
section_title: Civil Rights Protection
paragraphs: Section 253 of Title 10 (previously section 333 of Title 10) permits the President to use the Armed Forces to suppress any "insurrection, domestic violence, unlawful combination, or conspiracy" if law enforcement is hindered within a state, and local law enforcement is unable to protect individuals, or if the unlawful action "obstructs the execution of the laws of the United States or impedes the course of justice under those laws." This section was enacted to implement the Fourteenth Amendment guarantee for equal protection. It does not require the request or even the permission of the governor of the affected state. 
The provision lay dormant after the end of Reconstruction until 1957, when President Eisenhower ordered a battle group of the 101 st Airborne Division into Little Rock and federalized the entire Arkansas National Guard in order to enforce a court order permitting nine black students to attend a previously white high school. The proclamation to disperse cited both sections 332 and 333 of Title 10, U.S. Code. By federalizing the Arkansas Guard, the President effectively deprived the governor of forces that had several days previously been used to enforce the governor's view of law and order. 
Presidents Kennedy and Johnson followed the Little Rock precedent to deal with resistance to court-ordered desegregation in a number of Southern states. In 1962, after the governor of Mississippi attempted to prevent black student James H. Meredith from registering at the University of Mississippi at Oxford, President Kennedy sought to enforce the court order with federal marshals. When marshals met with resistance from state forces and later a riotous mob, President Kennedy federalized the Mississippi National Guard and ordered active Army troops already gathered in the area to take action. The President's proclamation to disperse named the governor and other state officials as forming the unlawful assemblies obstructing the enforcement of the court order, citing as authority both sections 332 and 333. President Kennedy followed a similar course of action to confront state resistance to court ordered desegregation in Alabama twice in 1963. President Johnson cited the same authority in 1965 to deploy troops, both regular Army and federalized National Guard, to Alabama to protect civil rights marchers as they made their way from Selma, AL, to Montgomery. 
section_title: Support to Law Enforcement
paragraphs: In 1981, Congress enacted general law enforcement exceptions to the Posse Comitatus Act prohibitions in order to resolve questions raised by the cases that grew out of the events at Wounded Knee. The take-over and events which occurred during the siege led to four cases involving a series of federal criminal charges including obstructing a law enforcement officer in the lawful performance of his duties during the course of a civil disturbance. Military assistance provided federal authorities at Wounded Knee undermined the prospects of a successful prosecution for obstructing law enforcement officers by casting doubt on whether they were performing their duties lawfully, an element necessary for conviction.
The 1981 legislation contains explicit grants of authority for military assistance to the police—federal, state, and local—particularly in the form of information and equipment, along with restrictions on the use of that authority. These exceptions are found in Chapter 15 of Title 10, U.S. Code, Military Support to Civilian Law Enforcement Agencies (§§271-284).
subsections: section_title: Information: Spies, Advisers, and Undercover Agents
paragraphs: The Wounded Knee cases spawned uncertainty as to the extent to which military authorities might share technical advice, the results of reconnaissance flights, or any other forms of information with civilian law enforcement authorities. Section 271 (previously Section 371) specifically permits the Armed Forces to share information acquired during military operations and in fact encourages the Armed Forces to plan their activities with an eye to the production of incidental civilian benefits. The section allows the use of military undercover agents and the collection of intelligence concerning civilian activities, however, only where there is a nexus to an underlying military purpose. The committee report suggested that the type of intelligence operations conducted by the Army in preparation for possible civil disturbances in previous decades was not meant to be authorized.
Section 273 (previously section 373) permits military personnel to train civilian police on "the operation and maintenance of equipment" and to provide them with "expert advice." The section was originally limited to equipment provided by the Armed Forces, but was expanded in 1988 to include training on any equipment regardless of its origin.
The explanation of what might constitute "expert advice" is limited, but Congress clearly did not use the phrase as a euphemism for active military participation in civilian police activity. 
An implementing regulation published in 2013 excludes certain intelligence activities from its purview. Under the regulation, assistance to law enforcement by Defense intelligence and counterintelligence components is permitted for purposes of investigating or preventing clandestine intelligence activities by foreign powers or international terrorist or narcotics activities. The provision also permits intelligence elements to cooperate with law enforcement agencies for protecting their own personnel, property, and information, and to provide specialized equipment, technical knowledge, or assistance of expert personnel when lives are endangered.
section_title: Equipment and Facilities
paragraphs: Abstractly it might seem that even civilian use—against Americans within the United States—of tanks, missiles, fighter planes, aircraft carriers, and other implements of war offends the Posse Comitatus Act even if use can be accomplished without the direct involvement of military personnel. The arsenal of American military weapons and equipment is "part of the Army and Air Force" even when turned over to civilian authorities before use for civilian purposes. Even if the Posse Comitatus Act were read to apply only to the use of personnel, would the use of military personnel to maintain equipment loaned to civilian authorities violate the act's proscription? The Wounded Knee cases provided conflicting answers.
The 1981 provisions make it clear that the Defense Department may provide civilian police with military equipment and under some circumstances, particularly in drug cases, may also supply military personnel to maintain and, for certain limited purposes (not including searches and seizures), operate such equipment. The provisions also include extraordinary authority to use Navy ships to support Coast Guard drug interdiction on the high seas. In 1996, Congress added authority for military assistance, including the provision of personnel and equipment, for the enforcement of laws prohibiting chemical and biological weapons of mass destruction. In 2015, Congress added authority for military assistance to the Department of Justice in the case of situations involving bombings of places of public use, government facilities, public transportation systems, and infrastructure facilities, including the use of ordinance disposal units. This authority does not permit the military to make arrests, directly participate in searches or seizures, or collect intelligence for law enforcement purposes. 
In 2016, Congress added authority for military support to counterdrug activities and activities to counter transnational organized crime. Under this authority, the Secretary of Defense is permitted to provide assistance for such purposes to any agency of the federal government or any state, local, tribal, or foreign law enforcement agency upon the request of an appropriate official. For assistance to domestic agencies, support is limited to maintenance and repair or upgrade of equipment on loan for such purposes; transportation of personnel and supplies and equipment; establishing operation of bases of operations or training facilities; training of law enforcement personnel in counterdrug or counter-transnational crime activities; detection, monitoring, and communication of the movement of air and sea traffic within 25 miles off the U.S. coast or surface traffic within 25 miles outside the geographic boundaries of the United States if such activities were initially detected outside the boundaries; construction of roads and fences and installation of lighting to block drug smuggling at international boundaries of the United States; establishment of command and control centers and computer networks to improve integration of participating agencies and units; linguist and intelligence analysis; and aerial and ground reconnaissance. With respect to support for foreign law enforcement agencies, the purposes are similar but somewhat more limited. In some cases, congressional notification is required.
section_title: Limitations: Military Preparedness, Reimbursement, and Direct Use
paragraphs: The authority granted in sections 271-284 is subject to three general caveats. It may not be used to undermine the military capability of the United States. The civilian beneficiaries of military aid must pay for the assistance. And, under section 275, the Secretary of Defense must issue regulations to ensure that the authority under the chapter does not result in use of the Armed Forces to make arrests or conduct searches and seizures solely for the benefit of civilian law enforcement.
For several years, the regulations called for by section 275 appeared in parallel form in the Code of Federal Regulations and in a Defense Department Directive. The heart of the regulations appeared in subsection 213.10(a)(3):
Except as otherwise provided in this enclosure, the prohibition on use of military personnel 'as a posse comitatus or otherwise to execute the laws' prohibits the following forms of direct assistance: 
(i) Interdiction of a vehicle, vessel, aircraft or other similar activity. 
(ii) A search or seizure. 
(iii) An arrest, stop and frisk, or similar activity. 
(iv) Use of military personnel for surveillance or pursuit of individuals, or as informants, undercover agents, investigators, or interrogators." 
Although the provisions were removed from the C.F.R., the directive remained in effect until 2013, when it was incorporated with civil disturbance authority and released as a DoD Instruction. A new C.F.R. was also issued in 2013, 32 C.F.R. part 182, which expanded the limitations to match those in the new Instruction, which provides that the following are prohibited:
(a) Interdiction of a vehicle, vessel, aircraft, or other similar activity.
(b) A search or seizure.
(c) An arrest; apprehension; stop and frisk; engaging in interviews, interrogations, canvassing, or questioning of potential witnesses or suspects; or similar activity.
(d) Using force or physical violence, brandishing a weapon, discharging or using a weapon, or threatening to discharge or use a weapon except in self-defense, in defense of other DoD persons in the vicinity, or in defense of non-DoD persons, including civilian law enforcement personnel, in the vicinity when directly related to an assigned activity or mission.
(e) Evidence collection; security functions; crowd and traffic control; and operating, manning, or staffing checkpoints.
(f) Surveillance or pursuit of individuals, vehicles, items, transactions, or physical locations, or acting as undercover agents, informants, investigators, or interrogators.
(g) Forensic investigations or other testing of evidence obtained from a suspect for use in a civilian law enforcement investigation in the United States unless there is a DoD nexus (e.g., the victim is a member of the Military Services or the crime occurred on an installation under exclusive DoD jurisdiction) or the responsible civilian law enforcement official requesting such testing declares in writing that the evidence to be examined was obtained by consent….
section_title: Military Purpose
paragraphs: The Armed Forces, when in performance of their military responsibilities, are beyond the reach of the Posse Comitatus Act and its statutory and regulatory supplements. Analysis of constitutional or statutory exceptions is unnecessary in such cases. The original debates make it clear that the act was designed to prevent use of the Armed Forces to execute civilian law. Congress did not intend to limit the authority of the Army to perform its military duties. The legislative history, however, does not resolve the question of whether the act prohibits the Army from performing its military duties in a manner that affords incidental benefits to civilian law enforcement officers.
The courts and commentators believe that it does not. As long as the primary purpose of an activity is to address a military purpose, the activity need not be abandoned simply because it also assists civilian law enforcement efforts. Courts appear to view the location of the activity as particularly indicative of primary purpose; as one court noted, "the power to maintain order, security, and discipline on a military facility is necessary for military operations."
The courts have concluded that, consistent with this legitimate military purpose to maintain order on military installations, military personnel may, without violating the Posse Comitatus Act, turn over to civilian law enforcement authorities armed felons arrested when they flee onto a military base, or drunk drivers arrested on a military base, or firearms stolen from a military installation, as well as any stolen equipment that belongs to a military unit. The courts have likewise found no violation of the act when military personnel arrest civilians on military facilities for crimes committed there, or when military authorities assist a civilian police investigation conducted on a military facility. The military purpose doctrine also permits military law enforcement personnel to investigate the off-base conduct of military personnel, and allows them to assist in investigating the off-base conduct of civilians who are suspected of involvement in a violation of the Uniform Code of Military Justice (UCMJ). The DOD Instruction evidences a comparable understanding.
Cases called to apply the military purpose doctrine in cooperative police activities occurring off-base are the most difficult to reconcile. Some seem to require no more than a logical military nexus; others demand a very clear, specific military connection before they will concede the presence of a military purpose; and still others seem to seek a middle ground.
Finally, it is arguable that Congress's authorization for the use of force against those responsible for the September 11 attacks has mooted some of the limitations on the use of the military for law enforcement purposes by recasting them as military operations. Soon after the attacks, the Office of Legal Counsel (OLC) advised the White House and Defense Department that the Posse Comitatus Act imposed no constraint on the President's use of military forces domestically for anti-terrorism operations against "international or foreign terrorists operating within the United States." This conclusion rested on the determination that the act
only applies to the domestic use of the Armed Forces for law enforcement purposes, rather than for the performance of military functions. The Posse Comitatus Act itself contains an exception that allows the use of the military when constitutionally or statutorily authorized, which has occurred in the present circumstances.
In concluding that the prevention and deterrence of terrorism is "fundamentally military, rather than law enforcement, in character," OLC conceded that distinguishing between military and law enforcement functions when dealing with terrorism is "no easy task." Counter-terrorism operations could therefore "resemble, overlap with, and assist ordinary law enforcement activity." 
Military action might encompass making arrests, seizing documents or other property, searching persons or places or keeping them under surveillance, intercepting electronic or wireless communications, setting up roadblocks, interviewing witnesses, and searching for suspects. Moreover, the information gathered in such efforts could be of considerable use to federal prosecutors if the Government were to prosecute against captured terrorists.
OLC further opined that the President's inherent power to defend the United States supplied a "constitutional exception" to the Posse Comitatus Act, and that statutory exceptions could be found in both the authorization for use of military force and section 333 (now section 253) of the Insurrection Act. 
It does not appear, however, that much of this opinion remains the official interpretation of the Justice Department. In 2008, OLC advised that "caution should be exercised before relying in any respect on the Memorandum [regarding the Authority for Use of Military Force to Combat Terrorist Activities Within the United States (Oct. 23, 2001) as a precedent of the Office of Legal Counsel," and that "certain propositions" stated therein "should not be treated as authoritative for any purpose." With respect to the discussion of the Posse Comitatus Act, the superseding memorandum criticized the 2001 memo as "far too general and divorced from specific facts and circumstances to be useful as an authoritative precedent of OLC." Rather than viewing the authorization statute as a statutory exception to the act, the successor memo believed it better to state that the "reasonable and necessary use of military force taken under the authority of the AUMF would be a military action, potentially subject to the established 'military purpose' doctrine, rather than a law enforcement action." Likewise, the revised view of the OLC emphasized that the use of the military to execute the law under the Insurrection Act "would require the presence of an actual obstruction of the execution of federal law or a breakdown in the ability of state authorities to protect federal rights."
The use of the military within the United States for counter-terrorism purposes has been negligible, despite some prodding from Congress to use military forces to apprehend, interrogate, and detain suspected members of Al Qaeda and "associated forces." Consequently, there is more commentary regarding the interplay of the Posse Comitatus Act and what was previously called the "Global War on Terror" than there are judicial decisions to test these theories. One U.S. citizen who was detained by the military without trial after having been designated an "enemy combatant" by the President sought habeas corpus relief, in part on the contention that his confinement by the military violated the Posse Comitatus Act. The reviewing district court judge saw things differently:
Padilla is not being detained by the military in order to execute a civilian law or for violating a civilian law, not-withstanding that his alleged conduct may in fact violate one or more such laws. He is being detained in order to interrogate him about the unlawful organization with which he is said to be affiliated and with which the military is in active combat, and to prevent him from becoming reaffiliated with that organization.
The decision, however, was reversed on the grounds that the detention violated a more specific statute, but was then vacated by the Supreme Court on procedural grounds. In subsequent proceedings, the petitioner did not rely on the Posse Comitatus Act. It seems safe to say, however, that if the Constitution does not stand in the way of such a measure, the Posse Comitatus Act will not likely impose a greater hurdle. 
section_title: Coverage of the Posse Comitatus Act
subsections: section_title: Willful Use
paragraphs: The act is limited to "willful" misuse of the Army or Air Force. The Senate version of the original act would have limited proscription to "willful and knowing" violations; the House version had no limitation. The compromise that emerged from conference opted to forbid only willful violations, but neither the statements of the managers nor statements elsewhere in the debate explain what the limitation means. In other instances, Congress has used the term "willful" in a number of different contexts and the term has been construed by the courts in a variety of ways, often inconsistent and contradictory. The scattered statements found in the case law under the act are somewhat conflicting and not particularly helpful, although it seems unlikely that a court would convict for anything less than a deliberate disregard of the law's requirements.
section_title: Execute the Law
paragraphs: When has the Army or Air Force been used "to execute the laws"? The language of the act by itself seems sweeping. It is comparable to the instruction of the Constitution that the President "take care that the laws are faithfully executed." Without more, it would seem to prohibit the use of the Army or the Air Force to implement the command or authorization of all state or federal law. It might apply with equal force to delivering the mail or making an arrest.
Existing case law and commentary indicate that "execution of the law" in violation of the Posse Comitatus Act occurs (a) when the Armed Forces perform tasks ordinarily assigned not to them but to an organ of civil government, or (b) when the Armed Forces perform tasks assigned to them solely for purposes of civilian government. (The test that applies in cases where military personnel or units are conducting activities in support of law enforcement authorities is somewhat different, and is covered below.)
While inquiries may surface in other contexts such as the use of the Armed Forces to fight forest fires or to provide assistance in the case of other natural disasters, Posse Comitatus Act questions arise most often when the Armed Forces assist civilian police. This is perhaps not surprising since it is the use that stimulated passage of the act. During the debate, Members complained of various ways in which the Army had been used, essentially as a police force, to break up labor disputes, to collect taxes, to execute search and arrest warrants, and to maintain order at the polls and during state legislative sessions.
At least when suggested that the Armed Forces have been improperly used as a police force, the tests used by most contemporary courts to determine whether military activity in support of civilian authorities violates the Posse Comitatus Act were developed out of disturbances at Wounded Knee on the Pine Ridge Indian Reservation in South Dakota and inquiry:
1. whether civilian law enforcement officials made a "direct active use" of military investigators to "execute the law"; 2. whether the use of the military "pervaded the activities" of the civilian officials; or 3. whether the military was used so as to subject "citizens to the exercise of military power which was regulatory, prescriptive, or compulsory in nature." 
The vast majority of cases called upon to apply these tests have found that the assistance provided civilian law enforcement did not constitute "execution of the law" in violation of Posse Comitatus Act requirements. Those most likely to fail the tests seem to be those where the activities appear to have a colorable military purpose, but the government fails to make a convincing showing.
The Office of Legal Counsel (OLC) opined in 1991 that the use of military personnel to conduct aerial infrared monitoring of private property for law enforcement purposes is "aerial reconnaissance" authorized by former 10 U.S.C. § 374(b)(2)(B), and is neither inconsistent with former 10 U.S.C. § 375 (assistance may not involve military personnel in search, seizure, or arrest) nor prohibited by the Posse Comitatus Act. To reach this conclusion, OLC relied on its interpretation of the legislative history of then-sections 371-375 to find that Congress did not mean the term "search" in former section 375 to include all conduct that would constitute a search under the Fourth Amendment. Rather, OLC found,
when Congress used the term "search" in section 375, it intended that the term encompass at most only searches involving physical contact with civilians or their property, and perhaps only searches involving physical contact that are likely to result in a direct confrontation between military personnel and civilians.
The legislative history suggested to OLC that Congress had intended to codify certain court decisions interpreting the Posse Comitatus Act to have as its primary aim the prevention of any "direct confrontation between military personnel and civilians."
section_title: Military Coverage
subsections: section_title: Navy & Marines
paragraphs: The Posse Comitatus Act proscribes use of the Army or the Air Force to execute the law. It says nothing about the Navy, the Marine Corps, the Coast Guard, or the National Guard. The amendment first offered to the Army appropriation bill in 1878 to enact the Posse Comitatus provisions would have prohibited use of "any part of the land or naval forces of the United States" to execute the law. Some commentators believe that sponsors subsequently limited the posse comitatus amendment to the Army appropriation bill in order to avoid challenges on grounds of germaneness. The courts have generally held that the Posse Comitatus Act by itself does not apply to the Navy or the Marine Corps. They maintain, however, that those forces are covered by similarly confining administrative and legislative supplements, the most currently applicable of which appear in the DOD Instruction.
section_title: Coast Guard
paragraphs: The Posse Comitatus Act likewise says nothing about the Coast Guard. The Coast Guard was formed by merging two civilian agencies, the Revenue Cutter Service and the Lifesaving Service. Although created and used for law enforcement purposes, the Cutter Service had already been used as part of the military forces of the United States by the time the Posse Comitatus Act was enacted.
The Coast Guard is now a branch of the Armed Forces, located within the Department of Homeland Security, but relocated within the Navy in time of war or upon the order of the President. The act does not apply to the Coast Guard while it remains part of the Department of Homeland Security. While part of the Navy, it is subject to the orders of the Secretary of the Navy, and consequently to any generally applicable directives or instructions issued under the Department of Defense or the Navy.
As a practical matter, however, the Coast Guard is statutorily authorized to perform law enforcement functions. Even while part of the Navy its law enforcement activities would come within the statutory exception to the posse comitatus restrictions, and the restrictions applicable to components of the Department of Defense would apply only to activities beyond those authorized.
section_title: National Guard
paragraphs: The act is silent as to what constitutes "part" of the Army or Air Force for purposes of proscription. There is little commentary or case law to resolve questions concerning the coverage of the National Guard, the Civil Air Patrol, civilian employees of the Armed Forces, or regular members of the Armed Forces while off duty.
Strictly speaking, the Posse Comitatus Act predates the National Guard only in name, for the Guard "is the modern Militia reserved to the States by Art. I, § 8, cls.15, 16, of the Constitution," which has become "an organized force, capable of being assimilated with ease into the regular military establishment of the United States." There seems every reason to consider the National Guard part of the Army or Air Force, for purposes of the Posse Comitatus Act, when in federal service. When not in federal service, historical reflection might suggest that it is likewise covered. Recall that it was the state militia, called to the aid of the marshal enforcing the Fugitive Slave Act, which triggered Attorney General Cushing's famous opinion. And that the Posse Comitatus Act's reference to "posse comitatus or otherwise" is a "they-are-covered-no-matter-what-you-call-them" response to the assertion derived from Cushing's opinion that troops could be used to execute the law as long as they were acting as citizens and not soldiers.
On the other hand, the National Guard is a creature of both state and federal law, a condition which as the militia it has enjoyed since the days of the Articles of Confederation. And the courts have said that members of the National Guard when not in federal service are not covered by the Posse Comitatus Act. Similarly, the DOD Instruction is only applicable to members of the National Guard when they are in federal service.
section_title: Off Duty Military, Acting as Citizens & Civilian Employees
paragraphs: The historical perspective fares little better on the question of whether the Posse Comitatus Act extends to soldiers who assist civilian law enforcement officials in a manner which any other citizen would be permitted to provide assistance, particularly if they do so while off duty.
Congress passed the act in response to cases where members of the military had been used based on their civic obligations to respond to the call as the posse comitatus. The debate in the Senate, however, suggests that the act was not intended to strip members of the military of all civilian rights and obligations.
The Senate debate may have influenced some reviewing courts, particularly in earlier decisions interpreting the Posse Comitatus Act, which held that a soldier who does no more than any other citizen might do to assist civilian law enforcement has not been used in violation of the Posse Comitatus Act. The more recent decisions under similar facts, with the endorsement of the commentators, have focused on the nature of the assistance provided and whether the assistance is incidental to action taken primarily for a military purpose.
Some have questioned whether civilian employees of the Armed Forces should come within the proscription of the act, but most, frequently without comment, seem to consider them "part" of the Armed Forces for purposes of the Posse Comitatus Act. The current Defense Department Instruction expressly applies "to civilian employees of the DoD Components and the activities of DoD contractors performed in support of the DoD Components." within its Posse Comitatus Act policy restrictions, while the Office of Legal Counsel considers that civilian employees are not "part of" the Armed Forces and may be assigned to duties with law enforcement organizations without violating the Posse Comitatus Act. The Office of Legal Counsel has also opined that military members who operate under civilian command and control are not "part of" the Armed Forces, at least so long as they are not still subject to the military chain of command.
section_title: Geographical Application
paragraphs: It seems unlikely that the Posse Comitatus Act, by itself, applies beyond the confines of the United States, its territories, and possessions. As a general rule, acts of Congress are presumed to apply only within the United States, its territories, and possessions unless Congress has provided otherwise or unless the purpose of Congress in enacting the legislation evidences an intent that the legislation enjoy extraterritorial application.
The Posse Comitatus Act contains no expression of extraterritorial application. Congress enacted it in response to problems occurring within the United States and its territories, problems associated with the American political process and military usurpation of civilian law enforcement responsibilities over Americans. It seems unlikely that its extraterritorial application was either anticipated or intended.
The first court to consider the question agreed, but it arose in occupied territory overseas in which an American military government had temporarily displaced civil authorities. For some time subsequent decisions either declined to resolve the issue or did not address it.
Congress does appear to have intended the authority and restrictions contained in 10 U.S.C. Sections 271-284 to apply both in the United States and beyond its borders. The provisions directing the placement of members of the Coast Guard on Navy ships for drug interdiction purposes evidence an understanding that the Posse Comitatus Act's statutory shadow, the restrictions on arrests and similar direct law enforcement activities under 10 U.S.C. Section 275, applies at least on the high seas. In some instances it initially contemplated that various provisions would only apply overseas.
The regulations implementing 10 U.S.C. Section 275 address only assistance to law enforcement officials of the several states, the United States, or its territories or possessions, but declares it does not apply to assistance to foreign officials. In the case of assistance provided overseas to foreign law enforcement officials, the so-called Mansfield Amendment creates something of an overseas version of the Posse Comitatus Act, at least for drug enforcement purposes.
section_title: Consequences of Violation
subsections: section_title: Prosecution
paragraphs: The Posse Comitatus Act is a criminal statute under which there has never been an officially reported prosecution, although it appears there were two prosecutions shortly after the act was passed. While some courts have concluded that it does not provide a private right of action on behalf of anyone who claims to have suffered some injury due to its violation, it has been invoked with varying degrees of success, as described below, to challenge the jurisdiction of the courts; as a defense in criminal prosecutions for other offenses; as a ground for the suppression of evidence; as the grounds for, or a defense against, civil liability; and as an impediment to proposed actions by the Armed Forces.
section_title: Exclusion of Evidence
paragraphs: Allegations that the Posse Comitatus Act has been violated are made most often by defendants seeking to exclude related testimony or physical evidence. The case law begins with United States v. Walden , where the U.S. Court of Appeals for the Fourth Circuit found that the Treasury Department's use of three Marines as undercover agents in an investigation of firearms offenses violated Navy regulations that made the act applicable to use of the Marines, but declined to order the exclusion of evidence obtained by the Marines.
The court found no "conscious, deliberate or willful intent on the part of the Marines or the Treasury Department's Special Investigator to violate" the regulation or the act. It also noted that the regulation contained no enforcement mechanism and the Posse Comitatus Act provided only for criminal prosecution, and that case before lacked the elements which had led to the adoption of the Fourth Amendment exclusionary rule. Finally, the court felt the use of the Marines had been aberrational; that subsequent similar transgressions were unlikely; and that the regulation would be amended to provide an enforcement component. But the court warned, "should there be evidence of widespread or repeated violations in any future case, or ineffectiveness of enforcement by the military, we will consider ourselves free to consider whether adoption of an exclusionary rule is required as a future deterrent."
Later defendants have focused upon the Walden court's warning; later courts have emphasized the refusal to adopt an exclusionary rule. Most cases note the absence of an exclusionary rule either to avoid deciding whether the Posse Comitatus Act was violated or to conclude that no relief is available irrespective of any violation. The U.S. Court of Appeals for the Ninth Circuit (Ninth Circuit) determined in one case that a Navy investigation of child pornography involving surveillance of all computers in the state of Washington, not merely limited to those with any connection to the military, amounted to impermissible direct active involvement in civilian enforcement of a widespread nature in violation of DoD regulations. A panel of the Ninth Circuit stated:
The government's position that the military may monitor and search all computers in a state even though it has no reason to believe that the computer's owner has a military affiliation would render the PCA's restrictions entirely meaningless. To accept that position would mean that NCIS agents could, for example, routinely stop suspected drunk drivers in downtown Seattle on the off-chance that a driver is a member of the military, and then turn over all information collected about civilians to the Seattle Police Department for prosecution.
Accordingly, the court found that "widespread and repeated violations" required deterrence and ordered evidence suppressed. However, the Ninth Circuit granted rehearing en banc and, while agreeing that the investigation violated regulations prohibiting direct military involvement in civilian law enforcement, held that the suppression of evidence was unnecessary to deter future violations where the government was already taking corrective action.
There being no clearly established right to the exclusion of evidence due to a violation of the Posse Comitatus Act, even if there is proof that violations are widespread, habeas petitioners have been unsuccessful in reversing their convictions based on a claimed violation. 
Three states' cases have required the suppression of evidence resulting from the use of military undercover agents to target civilian drug dealing without establishing any connection to activities on a military installation or sales to military personnel other than the undercover agents. Where the defendant is a member of the armed services and military investigators take part in an investigation, it has been held that an attorney's failure to make an effort to exclude evidence on the basis of an alleged Posse Comitatus Act violation does not give rise to a claim for ineffective assistance of counsel. 
section_title: Jurisdiction & Criminal Defenses
paragraphs: The first criminal defendants to seek refuge in the Posse Comitatus Act claimed unsuccessfully that use of the military to transport them back to the United States for trial violated the act and vitiated the jurisdiction of American courts to try them. Ordinarily, criminal trials are not barred simply because the defendant was unlawfully seized and carried into the jurisdiction of the trial court. There are indications that the same rule applies when the defendant challenges the court's jurisdiction on the grounds of Posse Comitatus Act violations. In the early posse comitatus cases, the defendants' arguments were further undermined by the fact that the countries from which they were returned, Germany and Japan, were under American military rule at the time. In later cases, some of which began beyond the territorial confines of the United States, although none in occupied territory, the courts noted that dismissal would not be an appropriate remedy for a posse comitatus violation. In one case, an effort to characterize the plea for dismissal as a request to be returned to the country of abduction for formal extradition was likewise held unavailing.
Defendants have found the act more helpful in prosecutions where the government must establish the lawfulness of its conduct as one of the elements of the offense charged, a rare feature of criminal prohibitions. Thus, several defendants at Wounded Knee were able to persuade the court that evidence of possible Posse Comitatus Act violations precluded their convictions for obstructing law enforcement officials "lawfully engaged" in the performance of their duties.
section_title: Civil Liability
paragraphs: Some time ago, the U.S. Court of Appeals for the Eighth Circuit found that a violation of the act might constitute an unreasonable search and seizure for purposes of the Fourth Amendment, thereby giving rise to a Bivens cause of action against offending federal officers or employees. A Posse Comitatus Act violation also provides the government with a defense to a claim under the Federal Tort Claims Act (FTCA) since the government is not liable under the FTCA for injuries inflicted by federal officers or employees acting outside the scope of their authority. It appears that plaintiffs asserting violations against state or local law enforcement officers also face an uphill battle. On balance, the Posse Comitatus Act is only rarely placed in issue in civil cases.
section_title: Compliance
paragraphs: The most significant impact of the Posse Comitatus Act is attributable to compliance by the Armed Forces. As administrative adoption of the act for the Navy and Marines demonstrates, the military has a long-standing practice of avoiding involvement in civilian affairs which it believes are contrary to the act.