Common law
Based on Wikipedia: Common law
The Law That Judges Make
Here's something that might surprise you: roughly one-third of the world's population lives under a legal system where judges, not legislators, created most of the rules. This isn't some ancient quirk that faded away with parchment scrolls. It's the foundation of law in the United States, the United Kingdom, Canada, Australia, India, and dozens of other countries. When you sign a contract, sue someone for negligence, or wonder whether your handshake deal is legally binding, you're often operating in a realm where the answers weren't written by any parliament or congress. They were hammered out by judges, case by case, over centuries.
This is common law.
What Makes Common Law Different
Most people assume that law comes from legislatures. Politicians debate, vote, and pass statutes that tell us what we can and cannot do. This is how civil law systems work, the kind you'd find in France, Germany, Japan, and most of continental Europe. In those places, comprehensive legal codes spell out the rules in advance, and judges apply them.
Common law works differently. It builds itself through decisions. When a dispute lands in court, the judge doesn't just consult a rulebook. Instead, the judge looks at how previous courts handled similar situations. Those earlier decisions become precedents, and precedents have a special power in common law jurisdictions: they bind future courts facing the same questions.
The Latin phrase for this principle is stare decisis, which translates roughly to "stand by things decided." It sounds formal, but the concept is intuitive. If a court in 1952 ruled that a certain business practice counts as fraud, a court in 2024 shouldn't suddenly declare the same practice perfectly legal. People need to be able to predict what the law will say, and that predictability comes from consistency.
But here's where it gets interesting: judges aren't absolutely locked into following every old decision. When circumstances change dramatically, or when a previous ruling proves unworkable or unjust, courts can distinguish the new case from the old one, or even overturn the precedent entirely. Common law breathes. It evolves.
A System Born from Conquest
The story begins in 1066, when William the Conqueror invaded England and defeated King Harold at the Battle of Hastings. The Normans who took over found a patchwork of local legal systems. Different regions had different customs, different courts, different ways of settling disputes. Shires and hundreds, the administrative units of Anglo-Saxon England, each ran their own folk courts. Landowners held private courts on their estates. Towns and merchant fairs had their own tribunals.
William and his successors wanted something more unified. Gradually, the king's courts began handling more cases, and as they did, they developed consistent practices. The law they applied became "common" in the sense that it was the same across all the king's courts throughout England, as opposed to the local variations that had come before.
This wasn't codification. Nobody sat down and wrote a comprehensive legal code. Instead, the common law emerged from the accumulation of judicial decisions, each one building on the ones before it. Lawyers and judges began keeping records of cases, first in manuscripts called yearbooks, later in printed law reports. These records became the raw material of the legal system, the archive that future courts would consult when facing new disputes.
England exported this system across its empire. Wales came first, then Ireland. The colonial expansion carried common law to North America, the Caribbean, Australia, New Zealand, South Africa, India, and beyond. When those colonies eventually became independent nations, most of them kept the legal framework they'd inherited. Today, the common law tradition shapes how law works for billions of people.
How Lawyers Actually Figure Out What the Law Says
In a civil law country, finding the applicable rule is relatively straightforward. You locate the relevant section of the code, read what it says, and apply it to your situation. In a common law system, the process is messier and more intellectually demanding.
First, you identify the facts of your situation. What actually happened? Who did what to whom, and when?
Then comes the research. You need to find relevant statutes, because common law jurisdictions do have legislation. But you also need to find cases, court decisions that dealt with similar facts. And not just any cases. You need to find the cases from courts whose decisions would actually bind the court where your dispute might be heard, or at least persuade that court.
This is where it gets complicated. Not all court decisions carry equal weight. In the American federal system, for instance, decisions from appellate courts bind the lower courts in their jurisdiction. If the Ninth Circuit Court of Appeals rules that a certain contract clause is enforceable, every federal district court from California to Alaska must follow that ruling. But a district court decision? That's merely persuasive. Another district court might find it interesting, even convincing, but it's not obligated to follow it.
The Supreme Court of the United States sits at the top of the federal hierarchy. Its decisions bind every federal court in the country. But even Supreme Court precedents aren't permanent. The court can overturn its own prior rulings, and it has done so many times throughout history, sometimes dramatically.
Once you've gathered your cases, you extract the principles. What did the courts say was important? What reasoning did they use? How might those principles apply to the facts you're dealing with? More recent decisions generally carry more weight than older ones. Higher courts trump lower courts. And through all of this, you're looking for patterns, trying to predict how a court would rule on your particular situation.
Oliver Wendell Holmes Jr., one of the most influential figures in American legal thought, captured something essential about this process. Legal principles in common law, he wrote, "arise gradually, in the emergence of a consensus from a multitude of particularized prior decisions." The law isn't handed down from above. It emerges from below, from the accumulated weight of countless individual judgments.
The Advantage of Gradual Evolution
Common law has a quality that legislation lacks: it can change slowly, almost imperceptibly, without the disruption of sudden shifts.
Getting a statute passed is enormously difficult. Someone has to draft a bill. It needs sponsors. It goes to committee, where it might languish for months or die quietly. If it survives committee, it faces debate, amendments, parliamentary maneuvering. It might need to pass both chambers of a legislature and be reconciled in conference. Then the executive has to sign it. The whole process is designed for deliberation, which often means paralysis.
Common law evolves through a different mechanism. Each case adjusts the law incrementally. A court might narrow a previous ruling slightly, or extend a principle to a new situation, or clarify an ambiguity that the earlier decision left unresolved. Over a decade, these small adjustments can produce significant change, but without any single moment of dramatic rupture. Businesses and individuals can adapt gradually because the law itself is changing gradually.
There's another advantage. Common law courts aren't absolutely bound by precedent. When a rule proves deeply unjust or hopelessly outdated, courts can overturn it. This power is exercised sparingly, with great reluctance, and usually only when the court can articulate extraordinarily compelling reasons. But the possibility exists. The law can correct its own mistakes without waiting for legislators to act.
When Statutes and Cases Collide
Statutes generally trump common law. If the legislature passes a law that contradicts a judicial precedent, the statute wins. Legislatures can codify common law rules they like, create entirely new legal rights that judges never recognized, or explicitly overrule court decisions they disagree with.
But the relationship is more subtle than simple hierarchy suggests.
There's an old maxim in American law: "Statutes in derogation of the common law ought to be narrowly construed." The idea is that when a statute takes away a right that the common law protected, courts should interpret that statute conservatively, giving maximum space to the common law principles that the legislature didn't explicitly abolish.
This maxim has fallen somewhat out of favor. Henry Campbell Black, who compiled the famous legal dictionary that bears his name, once wrote that the canon "no longer has any foundation in reason." Critics associated it with the Lochner era, that period in the early twentieth century when courts used various doctrines to strike down progressive economic legislation. But the underlying instinct persists in a more modest form: courts assume that legislatures don't intend to upend longstanding legal principles unless they say so clearly.
The Supreme Court has articulated this more carefully. Statutes "which invade the common law," the court has said, "are to be read with a presumption favoring the retention of long-established and familiar principles, except when a statutory purpose to the contrary is evident." When Congress legislates, it doesn't write on a blank slate. The common law is already there, and to displace it, the statute must "speak directly" to the question the common law had addressed.
Consider a concrete example. In 1877, the Supreme Court considered whether a Michigan statute establishing rules for marriage ceremonies had abolished common-law marriage, the practice of becoming legally married simply by living together and holding yourselves out as spouses, without any formal ceremony. The court said no. The statute required ceremonies for some purposes, but it didn't affirmatively prohibit common-law marriage or declare such unions invalid. The common law survived in the statute's silence.
Why Everyone Picks New York
If you've ever looked closely at a commercial contract, especially one involving large sums of money or international parties, you've probably noticed a clause near the end specifying that the agreement shall be governed by the laws of the State of New York.
This happens even when neither party has any connection to New York. Companies in Japan and Germany, parties from France and Brazil, businesses operating entirely in California or Texas, they all routinely choose New York law to govern their contracts. Why?
The answer reveals something important about how common law systems work.
New York has been America's commercial center for over two centuries. Its courts have been handling sophisticated business disputes for generations. As a result, New York has developed an extraordinarily deep body of commercial common law. Almost any question a contract might raise, some New York court has probably addressed it. The principles are well-established, the boundaries are clear, the outcomes are predictable.
Predictability is the key. Justice Louis Brandeis once wrote that "in most matters it is more important that the applicable rule of law be settled than that it be settled right." He wasn't being cynical. He was recognizing that people, especially commercial parties, need to be able to plan. They need to know what they can and cannot do. A clear rule, even an imperfect one, is often more valuable than uncertainty about what the perfect rule might be.
Common law systems excel at generating this predictability. Because courts must follow precedent, and because their decisions are published and available, lawyers can research almost any legal question and find reasonably precise guidance. Parties can structure their transactions with confidence that they understand the legal implications. They can approach the boundaries of what's permitted without accidentally crossing into illegality.
The same dynamic explains why American corporations so often incorporate in Delaware. It's a tiny state, but its courts have been handling corporate law disputes for so long that the answers to almost any question about shareholder rights, mergers and acquisitions, or fiduciary duties are already established somewhere in the case law. That depth attracts more companies, which generates more cases, which creates even more legal clarity. Success compounds.
The Price of Weak Precedent
Not all legal systems give precedent the same weight. In jurisdictions where courts feel free to decide each case fresh, without much concern for what earlier courts did, legal questions get relitigated constantly. The same issue might come out differently in front of different judges, or even in front of the same judge on different days.
This creates problems. Litigation becomes longer and more expensive because parties can't rely on written precedents to predict outcomes. Settlements become harder to reach because each side can point to decisions supporting their position. Businesses hesitate to invest because they can't be sure how courts will interpret their contracts or evaluate their conduct.
The contrast isn't hypothetical. Some civil law jurisdictions have experimented with giving more weight to judicial decisions, recognizing the practical benefits of consistency. And some common law jurisdictions have weakened their commitment to stare decisis, with visible effects on predictability and efficiency.
The Circuits and Their Conflicts
The American federal court system creates a distinctive pattern of precedent that's worth understanding.
Below the Supreme Court sit thirteen federal courts of appeals. Twelve of them cover geographic regions called circuits. The First Circuit handles appeals from Maine, Massachusetts, New Hampshire, Rhode Island, and Puerto Rico. The Ninth Circuit covers a vast western territory from California to Alaska. And so on. The thirteenth, the Court of Appeals for the Federal Circuit, handles appeals in patent cases and certain claims against the federal government regardless of geography.
Each circuit develops its own body of precedent. Decisions from the Fifth Circuit bind federal district courts in Texas, Louisiana, and Mississippi, but they're merely persuasive in federal courts elsewhere. A district court in Oregon follows Ninth Circuit precedent, not Fifth Circuit precedent.
This creates the possibility of circuit splits. The Fifth Circuit might rule that a certain type of contract clause violates federal law, while the Second Circuit rules that the same kind of clause is perfectly fine. Both rulings stand in their respective territories. Businesses operating nationally face genuine uncertainty: the same conduct might be legal in New York and illegal in Texas.
The Supreme Court exists in part to resolve these conflicts. When the circuits disagree on important questions, the Supreme Court can take a case and establish a uniform national rule. But the court can only hear a tiny fraction of the cases that parties ask it to review. Many circuit splits persist for years before the court addresses them, and some never get resolved at all.
Most federal appeals courts almost always sit in panels of three judges rather than with all their judges together. This creates its own complexity. What happens when two different three-judge panels from the same circuit reach conflicting conclusions? Generally, the earlier panel decision controls. A later panel can't overrule an earlier one. To overturn precedent, the full court must sit together, what lawyers call sitting "en banc," and rehear the issue.
The Supreme Court works differently. It always sits with all nine justices. A later decision simply supersedes an earlier conflicting one, and older precedents survive only to the extent they remain consistent with newer rulings. This sounds more straightforward, and in some ways it is. But it means that Supreme Court precedents are only as stable as the current majority's commitment to them. When the court's composition changes, interpretations that seemed settled can become vulnerable.
The Fiction of Ancient Wisdom
For centuries, lawyers and judges told themselves a story about where common law came from. The story went like this: the common law wasn't really judge-made. It was the accumulated wisdom of the Anglo-Saxon ancestors, ancient customs that judges merely discovered and declared. William Blackstone, the great eighteenth-century legal commentator, articulated this view influentially. Judges, in his telling, didn't make law. They found it.
This was always somewhat fictitious. If the law merely restated ancient custom, why did it keep changing? Why did courts so often need to address "cases of first impression," situations where no precedent existed? And who decided what the ancient customs actually were?
Jeremy Bentham saw through the pretense. He coined the term "judge-made law" precisely as a criticism, to strip away the mystification and reveal what was actually happening: judges were creating legal rules through their decisions, not channeling some pre-existing body of customary wisdom.
By the late nineteenth and early twentieth centuries, legal thinkers increasingly accepted Bentham's view, at least descriptively. Oliver Wendell Holmes, who would serve on the Supreme Court for three decades, was characteristically blunt. Judges, he wrote, "do and must legislate." They have no choice. When a case presents a question the law hasn't previously answered, the judge must answer it somehow, and that answer becomes law.
This acknowledgment made the common law more intellectually honest but also more controversial. If judges are making law, shouldn't that be the job of elected legislators? What legitimacy does an unelected judge have to impose new legal rules on the public?
The tension has never fully resolved. Common law systems have developed various doctrines to manage it: deference to legislative supremacy, narrow interpretations of judicial power, procedural requirements that limit when courts can reach certain questions. But at some fundamental level, the common law is judge-made law. That's what it is. That's what it has always been, despite the stories lawyers told themselves for centuries.
Still Standing After a Thousand Years
The common law tradition has proven remarkably durable. It survived the decline of the British Empire that spread it around the world. It adapted to democratic governance, constitutional limitations, and the rise of comprehensive statutory regulation. It absorbed centuries of social change, from feudalism to industrial capitalism to the digital economy.
Contract law and tort law, two of the largest areas of private law, still operate primarily on common law principles in jurisdictions like the United States and the United Kingdom. When you sue someone for breach of contract or for negligence, you're invoking doctrines that judges developed over centuries. The rules might be modified by statutes here and there, but the basic framework emerged from case law.
That framework offers something valuable: a method for developing legal rules through practical experience rather than theoretical abstraction. Each case presents real facts, real disputes, real human problems. The rules that emerge from deciding those cases have been tested against reality. Justice Benjamin Cardozo captured this quality when he noted that common law "does not work from pre-established truths of universal and inflexible validity to conclusions derived from them deductively." Instead, "its method is inductive, and it draws its generalizations from particulars."
Theory follows practice. Abstraction follows experience. The law learns what works by trying it.
This is slower than simply writing a code, but it may also be wiser. The common law, for all its complexity and occasional frustration, encodes centuries of accumulated judgment about how disputes should be resolved. That's not nothing. In fact, for roughly two billion people living under its principles, it's the foundation of legal order itself.