Common law

In common law legal systems, the law is created and/or refined by judges: a decision in the case currently pending depends on decisions in previous cases and affects the law to be applied in future cases. When there is no authoritative statement of the law, common law judges have the authority and duty to "make" law by creating precedent. The body of precedent is called "common law" and it binds future decisions. In future cases, when parties disagree on what the law is, an "ideal" common law court looks to past precedential decisions of relevant courts. If a similar dispute has been resolved in the past, the court is bound to follow the reasoning used in the prior decision (this principle is known as stare decisis). If, however, the court finds that the current dispute is fundamentally distinct from all previous cases, it will decide as a " matter of first impression." Thereafter, the new decision becomes precedent, and will bind future courts under the principle of stare decisis.

In practice, common law systems are considerably more complicated than the "ideal" system described above. The decisions of a court are binding only in a particular jurisdiction, and even within a given jurisdiction, some courts have more power than others. For example, in most jurisdictions, decisions by appellate courts are binding on lower courts in the same jurisdiction and on future decisions of the same appellate court, but decisions of non-appellate courts are only non-binding persuasive authority. Interactions between common law, constitutional law, statutory law and regulatory law also give rise to considerable complexity. However stare decisis, the principle that similar cases should be decided according to similar rules, lies at the heart of all common law systems.

Common law legal systems are in widespread use, particularly in those nations which trace their legal heritage to Britain, including the United Kingdom, most of the United States and Canada, and other former colonies of the British Empire.

Primary definitions

There are three main connotations to the term common law, and several historical ones worth mentioning:

1. Common law as opposed to statutory law and regulatory law: This connotation distinguishes the authority that promulgated a law. For example, in most areas of law in most jurisdictions in the United States, there are " statutes" enacted by a legislature, "regulations" promulgated by executive branch agencies pursuant to a delegation of rule-making authority from a legislature, and common law or " case law", i.e. decisions issued by courts (or quasi-judicial tribunals within agencies). This first connotation can be further differentiated, into (a) laws that arise purely from the common law with no express statutory authority, e.g. most criminal law and procedural law before the 20th century, and even today, most of contract law and the law of torts, and (b) decisions that discuss and decide the fine boundaries and distinctions in written laws promulgated by other bodies, such as the Constitution, statutes and regulations. See statutory law and non-statutory law.

2. Common law legal systems as opposed to civil law legal systems: This connotation differentiates "common law" jurisdictions and legal systems from "civil law" or " code" jurisdictions. Common law systems place great weight on court decisions, which are considered "law" just as are statutes. By contrast, in civil law jurisdictions (the legal tradition that prevails in, or is combined with common law, in almost all non-Islamic, non-common law countries), judicial precedent is given less weight, and contributions by scholars are given more. For example, the Napoleonic code expressly forbade French judges from pronouncing the law.

3. Law as opposed to equity: This connotation differentiates "common law" (or just "law") from " equity". Before 1873, England had two parallel court systems, courts of "law" that could only award money damages and recognized only the legal owner of property, and courts of "equity" that could issue injunctive relief and recognized trusts of property. This split propagated to many of the colonies, including the United States (see "Reception Statutes," below). The distinction between "law" and "equity" was important in (a) categorising and prioritizing rights to property, (b) determining whether the Seventh Amendment's right to a jury trial applies (a determination of a fact necessary to resolution of a "common law" claim) or whether the issue may be decided by a judge (issues of what the law is, and all issues relating to equity), and (c) in the principles that apply to the grant of equitable remedies by the courts. For most purposes, most jurisdictions, including those within the US, have merged the two courts. Additionally, even before the separate courts were merged together, most courts were permitted to apply both law and equity (though under potentially different laws of procedure). Even so, the split survives and remains relevant for determining at least these three classes of issues. Other exceptions are discussed in "Common Law Systems," below.

4. Historical uses: In addition, there are several historical uses of the term that provide some background as to its meaning. The English Court of Common Pleas dealt with lawsuits in which the king had no interest, i.e. between commoners. Additionally, from at least the 11th century and continuing for several centuries after that, there were several different circuits in the royal court system, served by itinerant judges who would travel from town to town dispensing the King's justice. The term "common law" was used to describe the law held in common between the circuits and the different stops in each circuit. The more widely a particular law was recognized, the more weight it held, whereas purely local customs were generally subordinate to law recognized in a plurality of jurisdictions. These definitions are archaic, their relevance having dissipated with the development of the English legal system over the centuries, but they do explain the origin of the term.

Basic principles of common law

Common law adjudication

In a common law jurisdiction, several stages of research and analysis are required to determine what "the law is" in a given situation. First, one must ascertain the facts. Then, one must locate any relevant statutes and cases. Then one must extract the principles, analogies and statements by various courts of what they consider important to determine how the next court is likely to rule on the facts of the present case. Later decisions, and decisions of higher courts or legislatures carry more weight than earlier cases and those of lower courts. Finally, one integrates all the lines drawn and reasons given, and determines what "the law is". Then, one applies that law to the facts.

The common law is more malleable than statutory law. First, common law courts are not absolutely bound by precedent, but can (when extraordinarily good reason is shown) reinterpret and revise the law, without legislative intervention, to adapt to new trends in political, legal and social philosophy. Second, the common law evolves through a series of gradual steps, that gradually works out all the details, so that over a decade or more, the law can change substantially but without a sharp break, thereby reducing disruptive effects. In contrast, the legislative process is very difficult to get started: legislatures do not act until a situation is totally intolerable. Because of this, legislative changes tend to be large, jarring and disruptive (either positively or negatively).

One example of the gradual change that typifies the common law is the gradual change in liability for negligence. For example, the traditional common law rule through most of the 19th century was that a plaintiff could not recover for a defendant's negligence unless the two were in privity of contract. Thus, only the immediate purchaser could recover for a product defect, and if a part was built up out of parts from parts manufacturers, the ultimate buyer could not recover for injury caused by a defect in the part. Winterbottom v. Wright, 10 M&W 109, 152 Eng.Rep. 402, 1842 WL 5519 (Exchequer of pleas 1842). In Winterbottom, the postal service had contracted with Wright to maintain its coaches. Winterbottom was a driver for the post. When the coach failed and injured Winterbottom, he sued Wright. The Winterbottom court recognized that there would be "absurd and outrageous consequences" if an injured person could sue any person peripherally involved, but could not find a good place to draw a line around the causal connection between the negligent conduct and the injury other than to limit liability to only the immediate person in contract with the negligent party. A first exception to this rule arose in Thomas v. Winchester, 6 N.Y. 397 (N.Y. 1852) which held that mislabeling a poison as an innocuous herb, and then selling the mislabeled poison through a dealer who would be expected to resell it, put "human life in imminent danger." Thomas used this as a reason to create an exception to the "privity" rule. In Statler v. Ray Mfg. Co., 195 N.Y. 478, 480 (N.Y. 1909) held that a coffee urn manufacturer was liable to a person injured when the urn exploded, because the urn "was of such a character inherently that, when applied to the purposes for which it was designed, it was liable to become a source of great danger to many people if not carefully and properly constructed."

Yet the privity rule survived. In Cadillac Motor Car Co. v Johnson, 221 F. 801 (2nd Cir. 1915) (decided by the federal appeals court for New York and several neighboring states), the court held that a car owner could not recover for injuries from a defective wheel, when the automobile owner only had a contract with the automobile dealer, not with the manufacturer, even though there was "no question that the wheel was made of dead and ‘dozy‘ wood, quite insufficient for its purposes."

Finally, in the famous case of MacPherson v. Buick Motor Co., 217 N.Y. 382, 111 N.E. 1050 (N.Y. 1916), Judge Cardozo pulled a broader principle out of these predecessor cases. The facts were almost identical to Cadillac a year earlier: a wheel from a wheel manufacturer was sold to Buick, to a dealer, to MacPherson, and the wheel failed, injuring MacPherson. Judge Cardozo held:

We hold, then, that the principle of Thomas v. Winchester is not limited to poisons, explosives, and things of like nature, to things which in their normal operation are implements of destruction. If the nature of a thing is such that it is reasonably certain to place life and limb in peril when negligently made, it is then a thing of danger. Its nature gives warning of the consequences to be expected. If to the element of danger there is added knowledge that the thing will be used by persons other than the purchaser, and used without new tests then, irrespective of contract, the manufacturer of this thing of danger is under a duty to make it carefully. ... There must be knowledge of a danger, not merely possible, but probable.

Note that Cardozo's new "rule" exists in no prior case, but is inferable as a synthesis of the principles stated in them, and represents a foreseeable progression. Importantly, note that Judge Cardozo continues to adhere to the original principle of Winterbottom, that "absurd and outrageous consequences" must be avoided, and he does so by drawing a new line in the last sentence quoted above: "There must be knowledge of a danger, not merely possible, but probable." But while adhering to the underlying principle, MacPherson overruled the rule of the prior common law by stating that privity was irrelevant.

Interaction of constitutional, statute and common law

In common law legal systems (connotation 2), the common law (connotation 1) is crucial to understanding almost all important areas of law. For example, in England and Wales and in most states of the United States, the basic laws of contracts, torts and property do not exist in statute, but only in common law (though there may be isolated modifications enacted by statute). In almost all areas of the law (even those where there is a statutory framework, such as contracts for the sale of goods, or the criminal law), other written laws generally give only terse statements of general principle, and the fine boundaries and definitions exist only in the common law (connotation 1). To find out what the precise law is that applies to a particular set of facts, one has to locate precedential decisions on the topic, and reason from those decisions by analogy. To consider but one example, the First Amendment to the United States Constitution states "Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof" – but interpretation (that is, determining the fine boundaries, and resolving the tension between the "establishment" and "free exercise" clauses) of each of the important terms was delegated by Article III of the Constitution to the judicial branch, so that the current legal boundaries of the Constitutional text can only be determined by consulting the common law.

In common law jurisdictions, legislatures operate under the assumption that statutes will be interpreted against the backdrop of the pre-existing common law case law and custom, and so may leave a number of things unsaid. For example, in most U.S. states, the criminal statutes are primarily codification of pre-existing common law. ( Codification is the process of enacting a statute that collects and restates pre-existing law in a single document - when that pre-existing law is common law, the common law remains relevant to the interpretation of these statutes.) In reliance on this assumption, modern statutes often leave a number of terms and fine distinctions unstated -- for example, a statute might be very brief, leaving the precise definition of terms unstated, under the assumption that these fine distinctions will be inherited from pre-existing common law. For this reason, even today American law schools teach the common law of crime as practised in England in 1789, because the backdrop of centuries-old English common law is necessary to interpret and fully understand the literal words of the modern criminal statute.

With the transition from English law, which had common law crimes, to the new legal system under the U.S. Constitution, which prohibited ex post facto laws at both the federal and state level, the question was raised whether there could be common law crimes in the United States. It was settled in the case of United States v. Hudson and Goodwin which decided that common law crimes were prohibited (at least at the Federal level), and that there must always be a (constitutional) statute defining the offense and the penalty for it.

By contrast to the statutory codifications of common law, some laws are purely statutory, and may create a new cause of action beyond the common law. An example is the tort of wrongful death, which allows certain persons, usually a spouse, child or estate, to sue for damages on behalf of the deceased. There is no such tort in English common law; thus, any jurisdiction that lacks a wrongful death statute will not allow a lawsuit for the wrongful death of a loved one. Where a wrongful death statute exists, the compensation or other remedy available is limited to the remedy specified in the statute (typically, an upper limit on the amount of damages). Courts generally interpret statutes that create new causes of action narrowly – that is, limited to their precise terms – because the courts generally recognize the legislature as being supreme in deciding the reach of judge-made law unless such statute should violate some "second order" constitutional law provision (cf. judicial activism).

Where a tort is rooted in common law, then all traditionally recognized damages for that tort may be sued for, whether or not there is mention of those damages in the current statutory law. For instance, a person who sustains bodily injury through the negligence of another may sue for medical costs, pain, suffering, loss of earnings or earning capacity, mental and/or emotional distress, loss of quality of life, disfigurement and more. These damages need not be set forth in statute as they already exist in the tradition of common law. However, without a wrongful death statute, most of them are extinguished upon death.

Contrasting role of treatises and academic writings in common law and civil law systems

In many subject matter areas, legal treatises compile common law decisions, and state overarching principles that (in the author's opinion) explain the results of the cases. However, in common law jurisdictions, treatises are not the law, and lawyers and judges tend to use these treatises as only "finding aids" to locate the relevant cases.

This is one of the "cultural" differences between common law and civil law jurisdictions (connotation 2): in civil law jurisdictions, the writings of law professors are given significant weight by courts. In common law jurisdictions, scholarly work is seldom cited as authority for what the law is. When common law courts rely on scholarly work, it is almost always only for factual findings, policy justification, or the history and evolution of the law, but the court's legal conclusion is reached through analysis of relevant statutes and common law, seldom scholarly commentary.

Common law as a foundation for commercial economies

This reliance on judicial opinion is a strength of common law systems, and is a significant contributor to the robust commercial systems in the United Kingdom and United States. Because there is common law to give reasonably precise guidance on almost every issue, parties (especially commercial parties) can predict whether a proposed course of action is likely to be lawful or unlawful. This ability to predict gives more freedom to come close to the boundaries of the law. For example, many commercial contracts are more economically efficient, and create greater wealth, because the parties know ahead of time that the proposed arrangement, though perhaps close to the line, is almost certainly legal. Newspapers, taxpayer-funded entities with some religious affiliation, and political parties can obtain fairly clear guidance on the boundaries within which their freedom of expression rights apply. In contrast, in non-common-law countries, fine questions of law are redetermined anew each time they arise, making consistency and prediction more difficult. Thus, in jurisdictions that do not have a strong allegiance to a large body of precedent, parties have less a priori guidance must often leave a bigger "safety margin" of unexploited opportunities.

This is the reason for the frequent choice of the law of the State of New York in commercial contacts from throughout the United States, and often in contracts from elsewhere in the world, even where the contacts of the parties and transaction to New York is quite attenuated. Because of its history as the nation's commercial centre, New York common law has a depth and predictability not (yet) available in any other jurisdiction.

History of the common law

England before 1600

Common law originally developed under the inquisitorial system in England during the 12th and 13th centuries, as the collective judicial decisions that were based in tradition, custom and precedent. Such forms of legal institutions and culture bear resemblance to those which existed historically in continental Europe and other societies where precedent and custom have at times played a substantial role in the legal process, including Germanic law recorded in Roman historical chronicles. The form of reasoning used in common law is known as casuistry or case-based reasoning. The common law, as applied in civil cases (as distinct from criminal cases), was devised as a means of compensating someone for wrongful acts known as torts, including both intentional torts and torts caused by negligence, and as developing the body of law recognizing and regulating contracts. The type of procedure practiced in common law courts is known as the adversarial system; this is also a development of the common law.

Before the Norman Conquest in 1066, justice was administered primarily by county courts, presided by the diocesan bishop and the sheriff, exercising both ecclesiastical and civil jurisdiction. Trial by jury started in these courts. There was a large role for unwritten local customs and enforcement could often be arbitrary.

In 1154, Henry II became the first Plantagenet king. Among many achievements, Henry institutionalized common law by creating a unified system of law "common" to the country through incorporating and elevating local custom to the national, ending local control and peculiarities, eliminating arbitrary remedies and reinstating a jury system – citizens sworn on oath to investigate reliable criminal accusations and civil claims. The jury reached its verdict through evaluating common local knowledge, not necessarily through the presentation of evidence, a distinguishing factor from today's civil and criminal court systems.

Henry II developed the practice of sending judges from his own central court to hear the various disputes throughout the country. His judges would resolve disputes on an ad hoc basis according to what they interpreted the customs to be. The king's judges would then return to London and often discuss their cases and the decisions they made with the other judges. These decisions would be recorded and filed. In time, a rule, known as stare decisis (also commonly known as precedent) developed, which is where a judge would be bound to follow the decision of an earlier judge; he was required to adopt the earlier judge's interpretation of the law and apply the same principles promulgated by that earlier judge if the two cases had similar facts to one another. By this system of precedent, decisions 'stuck' and became ossified, and so the pre-Norman system of disparate local customs was replaced by an elaborate and consistent system of laws that was common throughout the whole country, hence the name, "common law."

Henry II's creation of a powerful and unified court system, which curbed somewhat the power of canonical (church) courts, brought him (and England) into conflict with the church, most famously with Thomas Becket, the Archbishop of Canterbury. Eventually, Becket was murdered inside Canterbury Cathedral by four knights who believed themselves to be acting on Henry's behalf. Whether Henry actually intended to bring about the assassination of Becket is doubtful, but there is no question that at the time of the murder, the two men were embroiled in a bitter dispute regarding the power of Royal Courts to exercise jurisdiction over former clergymen. The murder of the Archbishop, who was immediately venerated as a martyr and later as a saint, gave rise to a wave of popular outrage against the King. Henry was forced to repeal the disputed laws and to abandon his efforts to hold church members accountable for secular crimes (see also Constitutions of Clarendon).

In spite of this setback, judge-made common law endured for centuries as the primary source of criminal and civil laws throughout the realm. Later, after Parliament acquired legislative powers, statutory law began to limit the scope of the common law in some areas. Even today, however, common law retains its status as an essential element of the British legal system.

Propagation of the Common Law to the colonies and commonwealth by Reception Statutes

Following the American Revolution, one of the first legislative acts undertaken by each of the newly independent states was to adopt "reception statutes" that gave legal effect to the existing body of English Common Law. Some states enacted reception statutes as legislative statutes, while other states received the English common law through provisions of the state's constitution.

For example, the New York Constitution of 1777 provides that:

“

[S]uch parts of the common law of England, and of the statute law of England and Great Britain, and of the acts of the legislature of the colony of New York, as together did form the law of the said colony on the 19th day of April, in the year of our Lord one thousand seven hundred and seventy-five, shall be and continue the law of this State, subject to such alterations and provisions as the legislature of this State shall, from time to time, make concerning the same.

”

Alexander Hamilton emphasized in The Federalist that this New York constitutional provision expressly made the common law subject “to such alterations and provisions as the legislature shall from time to time make concerning the same.” Thus, even when reception was effected by a constitution, the common law was still subject to alteration by a legislature's statute.

The Northwest Ordinance, which was approved by the Congress of the Confederation in 1787, guaranteed "judicial proceedings according to the course of the common law." Nathan Dane, the primary author of the Northwest Ordinance, viewed this provision as a default mechanism in the event that federal or territorial statutes were silent about a particular matter; he wrote that if "a statute makes an offence, and is silent as to the mode of trial, it shall be by jury, according to the course of the common law.” In effect, the provision operated as a reception statute, giving legal authority to the established common law in the vast territories where no states had yet been established.

Over time, as new states were formed from federal territories, these territorial reception statutes became obsolete and were re-enacted as state laws. For example, a reception statute enacted by legislation in the state of Washington requires that "[t]he common law, so far as it is not inconsistent with the Constitution and laws of the United States, or of the state of Washington nor incompatible with the institutions and condition of society in this state, shall be the rule of decision in all the courts of this state." In this way, the common law was eventually incorporated into the legal systems of every state except Louisiana (which inherited its civil law system from France).

A similar statute exists in Article 8 of the Basic Law of Hong Kong.

1870 through 20th century, and the Merger of Law and Equity

As early as the 15th century, it became the practice that litigants who felt they had been cheated by the common-law system would petition the King in person. For example, they might argue that an award of damages (at common law) was not sufficient redress for a trespasser occupying their land, and instead request that the trespasser be evicted. From this developed the system of equity, administered by the Lord Chancellor, in the courts of chancery. By their nature, equity and law were frequently in conflict and litigation would frequently continue for years as one court countermanded the other, even though it was established by the 17th century that equity should prevail. A famous example is the fictional case of Jarndyce and Jarndyce in Bleak House, by Charles Dickens.

In England, courts of law and equity were combined by the Judicature Acts of 1873 and 1875, with equity being supreme in case of conflict.

In the United States, parallel systems of law (providing money damages, with cases heard by a jury upon either party's request) and equity (fashioning a remedy to fit the situation, including injunctive relief, heard by a judge) survived well into the 20th century. The United States federal courts procedurally separated law and equity: the same judges could hear either kind of case, but a given case could only pursue causes in law or in equity, and the two kinds of cases proceeded under different procedural rules. This became problematic when a given case required both money damages and injunctive relief. In 1937, the new Federal Rules of Civil Procedure combined law and equity into one form of action, the "civil action." Fed.R.Civ.P. 2. The distinction survives to the extent that issues that were "common law" as of 1791 (the date of adoption of the Seventh Amendment) are still subject to the right of either party to request a jury, and "equity" issues are decided by a judge.

Alabama, Delaware, Mississippi and New Jersey still have separate courts of law and equity, for example, the Court of Chancery. In many states there are separate divisions for law and equity within one court.

Common law legal systems

The common law constitutes the basis of the legal systems of: England and Wales, Northern Ireland, the Republic of Ireland, federal law in the United States and the states' laws (except Louisiana), federal law in Canada and the provinces' laws (except Quebec civil law), Australia (both federal and individual states), New Zealand, South Africa, India, Malaysia, Brunei, Pakistan, Singapore, Hong Kong, and many other generally English-speaking countries or Commonwealth countries (except Malta and Scotland and the Canadian province of Quebec)). Essentially, every country which has been colonised at some time by England, Great Britain, or the United Kingdom uses common law except those that had been formerly colonised by other nations, such as Quebec (which follows French law to some extent), South Africa and Sri Lanka (which follow Roman Dutch law), where the prior civil law system was retained to respect the civil rights of the local colonists. India's system of common law is also a mixture of English law and the local Hindu law, except in the state of Goa which retains the Portuguese civil code. Nicaragua's legal system also is a mixture of the English Common Law and the Civil Law through the influence of British administration of the Eastern half of the country from the mid-1600's until about 1905, the William Walker period from about 1855 through 1857, USA interventions/occupations during the period from 1909 to 1933, the influence of USA institutions during the Somoza administrations (1933 through 1979) and the considerable importation between 1979 and the present of USA culture and institutions.

The main alternative to the common law system is the civil law system, which is used in Continental Europe, and most of the rest of the world. The former Soviet Bloc and other Socialist countries used a Socialist law system.

The opposition between civil law and common law legal systems has become increasingly blurred, with the growing importance of jurisprudence (almost like case law but in name) in civil law countries, and the growing importance of statute law and codes in common law countries (for example, in matters of criminal law, commercial law (the Uniform Commercial Code in the early 1960s) and procedure (the Federal Rules of Civil Procedure in the 1930s and the Federal Rules of Evidence in the 1970s)).

Scotland is often said to use the civil law system but in fact it has a unique system that combines elements of an uncodified civil law dating back to the Corpus Juris Civilis with an element of common law long predating the Treaty of Union with England in 1707 (see Legal institutions of Scotland in the High Middle Ages). Scots common law differs in that the use of precedents is subject to the courts seeking to discover the principle which justifies a law rather than to search for an example as a precedent and that the principles of natural justice and fairness have always formed a source of Scots Law. Comparable pluralistic (or 'mixed') legal systems operate in Quebec, Louisiana and South Africa.

Israel has a mixed system of common law and civil law. While Israeli law is undergoing codification, its basic principles resemble those of British and American law, namely: the role of courts in creating the body of law and the authority of the supreme court in overturning legislative and executive decisions.

The U.S. state of California has a system based on common law, but it has codified the law in the manner of the civil law jurisdictions. The reason for the enactment of the codes in California in the nineteenth century was to replace a pre-existing system based on Spanish civil law with a system based on common law, similar to that in most other states. California and a number of other Western states, however, have retained the concept of community property derived from civil law. The California courts have treated portions of the codes as an extension of the common-law tradition, subject to judicial development in the same manner as judge-made common law. (Most notably, in the case Li v. Yellow Cab Co., 13 Cal.3d 804 (1975), the California Supreme Court adopted the principle of comparative negligence in the face of a California Civil Code provision codifying the traditional common-law doctrine of contributory negligence.)

The state of New York, which also has a civil law history from its Dutch colonial days, also began a codification of its laws in the 19th century. The only part of this codification process that was considered complete is known as the Field Code applying to civil procedure. The original colony of New Netherlands was settled by the Dutch and the law was also Dutch. When the English captured pre-existing colonies they continued to allow the local settlers to keep their civil law. However, the Dutch settlers revolted against the English and the colony was recaptured by the Dutch. When the English finally regained control of New Netherland they forced, as a punishment unique in the history of the British Empire, the English common law upon all the colonists, including the Dutch. This was problematic, as the patroonsystem of land holding, based on the feudal system and civil law, continued to operate in the colony until it was abolished in the mid-nineteenth century. The influence of Roman Dutch law continued in the colony well into the late nineteenth century. The codification of a law of general obligations shows how remnants of the civil law tradition in New York continued on from the Dutch days.

The United States federal government (as opposed to the states) has a variant on a common law system. United States federal courts only act as interpreters of statutes and the constitution (to elaborate and precisely define the broad language, connotation 1(b) above), but, unlike state courts, do not act as an independent source of common law (connotation 1(a) above). Before 1938, the federal courts, like almost all other common law courts, decided the law on any issue where the relevant legislature (either the U.S. Congress or state legislature, depending on the issue), had not acted, by looking to courts in the same system, that is, other federal courts, even on issues of state law, and even where there was no express grant of authority from Congress or the Constitution. In 1938, the U.S. Supreme Court in Erie Railroad Co. v. Tompkins 304 U.S. 64, 78 (1938), overruled earlier precedent, and held "There is no federal general common law," thus confining the federal courts to act only as interpreters of law originating elsewhere. E.g., Texas Industries v. Radcliff, 451 U.S. 630 (1981) (without an express grant of statutory authority, federal courts cannot create rules of intuitive justice, for example, a right to contribution from co-conspirators). Post-1938, federal courts deciding issues that arise under state law are required to defer to state court interpretations of state statutes, or reason what a state's highest court would rule if presented with the issue, or to certify the question to the state's highest court for resolution. Later courts have limited Erie slightly, to create a few situations where United States federal courts are permitted to create federal common law rules without express statutory authority, for example, where a federal rule of decision is necessary to protect uniquely federal interests. See, e.g., Clearfield Trust Co. v. United States, 318 U.S. 363 (1943) (giving federal courts the authority to fashion common law rules with respect to issues of federal power, in this case negotiable instruments backed by the federal government); see also International News Service v. Associated Press, 248 U.S. 215 (1918) (creating a cause of action for misappropriation of "hot news" that lacks any statutory grounding, but that is one of the handful of federal common law actions that survives today). Except on Constitutional issues, Congress is free to legislatively overrule federal courts' common law.

Works on the common law

The definitive historical treatise on the common law is Commentaries on the Laws of England, written by Sir William Blackstone and first published in 1765 - 1769. Since 1979 a facsimile edition of that first edition has been available in four paper-bound volumes. Today it has been superseded in the English part of the United Kingdom by Halsbury's Laws of England that covers both common and statutory English law.

While he was still on the Massachusetts Supreme Judicial Court, and before being named to the U.S. Supreme Court, Justice Oliver Wendell Holmes Jr. published a short volume called The Common Law which remains a classic in the field. Unlike Blackstone and the Restatements, Holmes' book only briefly discusses what the law is; rather, Holmes describes the common law process.

In the United States, Restatements of various subject matter areas (Contracts, Torts, Judgments, etc.), edited by the American Law Institute, collect the common law for the area. The ALI Restatements are often cited by American courts and lawyers for propositions of uncodified common law, and are considered highly-persuasive authority, just below binding precedential decisions. The Corpus Juris Secundum is an encyclopedia whose main content is a compendium of the common law and its variations throughout the various state jurisdictions.

Scots common law covers matters including murder and theft, and has sources in custom, in legal writings and previous court decisions. The legal writings used are called Institutional Texts and come mostly from the 17th, 18th and 19th centuries. Examples include Craig, Jus Feudale (1655) and Stair, The Institutions of the Law of Scotland (1681).