Americans have a tradition, born in England and developed in the early years of our nation, thatrebels against military involvement in civilian affairs. It finds its most tangible expression in thenineteenth century Posse Comitatus Act, 18 U.S.C. 1385. The Act forbids use of the Army and AirForce to execute civil law except where expressly authorized. The exception documents a contrary component of the tradition. It accepts the use of the armed forces in extraordinary circumstances if expressly approved by Congress. Striking the balancebetween rule and exception has never been easy, but failure to do so has often proven unfortunate. When the rule is too unforgiving, a Shays's Rebellion may go unchecked. When exceptions are toogenerously granted, a Boston Massacre or Kent State tragedy may follow. Several times in the recent past, concerns that civil authorities may be overwhelmed by threats of natural disasters, civil disturbances, drug trafficking, and terrorism have produced calls for moregenerous exceptions to the rule. Some of those calls have been answered, others have not. This isan effort to sketch the current state of the law. The Magna Carta gives us the first recorded acknowledgment of the origins of theAnglo-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 legaljudgment of his peers or by the law of the land." (1) Subsequent legislation in the reign of Edward IIIexplained that this precluded punishment by the King except "in due Manner . . . or by Process madeby Writ. . . [or] by Course of the Law," (2) or as latermore simply stated, except "by due Process of theLaw." (3) Three hundred years after the passage of theEdwardian statutes, Lord Coke and othermembers of Parliament read these due process and law of the land requirements to include a broadprohibition against the use of martial law in peacetime, an interpretation they compelled KingCharles I to acknowledge. (4) King Charles I, preparing for a military expedition in France, had quartered his troops in homes along the southern English coastline. (5) Riotingresulted, and the participants, both military andcivilian, 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 soughtand was granted the Petition of Right of 1628 which outlawed both quartering and martial lawcommissions. (6) 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. Theircircumstances, however, were not exactly identical to those surrounding the Petition of Right. First,the question arose in the colonies. England had stationed troops in the colonies to protect themagainst 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 ratherthan military justice, and soldiers who employed more force than civilian law permitted werethemselves subject to civilian justice as the trials of the soldiers involved in the Boston Massacredemonstrates. 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, notto accomplish the transition between civil governments within a conquered territory as they had beenafter the French lost Canada to the British as a consequence of those conflicts, but as an independentmilitary force quartered among a disgruntled civilian population to police it. (7) 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 Militaryindependent of and superior to the civil power," and had "quarter[ed] large bodies of armed troopsamong us . . . protecting them, by a mock trial, from punishment for any murders which they shouldcommit on the inhabitants of these States." (8) The Articles of Confederation addressed the threat of military intrusion into civilian affairs by demanding that the armed forces assembled during peacetime be no more numerous than absolutelynecessary for the common defense, by entrusting control to civil authorities within the states, andby a preference for the farmer in arms as a member of the militia over the standing professionalarmy. (9) 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 theArmy and Navy of the United States and that civilian authorities, the Congress, should be solelyempowered to raise and support Armies, provide and maintain a Navy, and make rules for theirgovernment and regulation. (10) The Bill of Rightslimited the quartering of troops in private homes,U.S.Const. Amend. III, and noted that "a well regulated Militia, being necessary to the security ofa free State, the right of the people to keep and bear Arms, shall not be infringed," U.S.Const.Amend. II. The Constitution, on the other hand, explicitly permitted the Congress to provide forcalling out the militia to execute the laws, suppress insurrection, and repel invasion, U.S.Const. Art.I,ï¿½8, cl.16. 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," andsubsequently in cases of invasion, insurrection, or obstruction of the laws. (11) Washington used this authority to put down the Whiskey Rebellion in Western Pennsylvania (12) and subsequent Presidents have relied upon it with some frequency for riot control or when inextreme cases they felt it necessary to ensure the execution of federal law. (13) The President's authority to call upon the state militia to aid in putting down insurrections is reminiscent of the authority enjoyed by the sheriff at common law to call upon the posse comitatus. (14) In the beginning the two were comparable but unrelated. Even though Congress empowered thePresident to call out the militia to overcome obstructions to law enforcement, it continued to vest thefederal equivalent of the sheriff, the federal marshal, with the power to call forth the posse comitatusin performance of his duties. (15) In some cases when it passed a particular statute Congress specifically authorized recourse to the posse comitatus for its enforcement. Under the Fugitive Slave Act, for instance, owners whoseslaves had escaped to another state were entitled to an arrest warrant for the slaves and to have thewarrant executed by the federal marshals. The marshals in turn might "summon and call to their aidthe 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 theirservices may be required, as aforesaid, for that purpose," 9 Stat. 462, 463 (1850). 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 toprevent abolitionists from rescuing the prisoner before he could be returned to his owner. Themarshal subsequently filed a claim with the Treasury of the United States for reimbursement of thefunds 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 theclaim. Cushing's response went well beyond the question of whether the "bystanders" contemplated by the Fugitive Slave Act might included members of a state militia when not in federal service, andannounced a broader principle -- members of the military by virtue of their duties as citizens werepart of the posse comitatus. He 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 themilitary of all denominations, militia, soldiers, marines, all of whom are alike bound to obeythe 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 legalcharacter. They are still the posse comitatus. (xxi Parl. Hist., p.672, 688, per Lord Mansfield). "6 Op.Att'y Gen. 466, 473 (1854). (16) 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 conflictbetween pro and anti-slavery forces in Kansas. Congress reacted with a rider to an Armyappropriations bill forbidding the use of any "part of the military forces of the United States toenforce territorial law in Kansas." (17) After somediscussion of whether the amendment was germane,it was defeated. 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 beenlifted.