What is Common Law?

Robinhood Learn
Democratize finance for all. Our writers’ work has appeared in The Wall Street Journal, Forbes, the Chicago Tribune, Quartz, the San Francisco Chronicle, and more.

Common law is a body of law composed of decisions made by judges in the past and used as an example in similar future cases.

🤔 Understanding common law

Common law (aka "case law") is a body of unwritten laws based on courts' practice and experience — A sort of backup solution when the written statutory law has no straightforward answer. It includes the history and detailed records of decisions made by judges in unusual cases when there was no clear legislation to apply. These prior decisions are known as legal precedents. The main principle that sustains the common law considers that once a question receives an answer in front of a court, the same response should be delivered for similar cases in the future. Common law is practiced in various countries of the world and sometimes is taken into consideration when new legislation is issued. The U.S. common law system grew out of the British tradition that spread to North America in the 1700s and 1800s.


Common-law marriage is one example of a well-known arrangement being covered by common law. In a common-law marriage, two people who cohabitate for a period of time (which varies by jurisdiction) and hold themselves out to the community as married, can potentially be legally considered to have the rights of spouses — even if they’ve never registered their marriage with the government. The body of law around this has grown out of court decisions over hundreds of years. The law surrounding common-law marriage differs across different jurisdictions.


Common law is like getting lost in the woods and using the signs of nature to find your way out...

Common law's purpose is to offer a solution when statutory law doesn't — or when relevant statutory law does not exist. In such cases, judges refer to precedents, meaning the judicial decision of previous, similar cases. It's kind of like when you are lost in the woods, and your phone is dead, so you need to find another tool to help you get out. You know you can find the direction based on the sun's position or by where the moss is growing on trees.

Ready to start investing?
Sign up for Robinhood and get your first stock on us.
Sign up for Robinhood
Certain limitations apply

The free stock offer is available to new users only, subject to the terms and conditions at rbnhd.co/freestock. Free stock chosen randomly from the program’s inventory. Securities trading is offered through Robinhood Financial LLC.

Tell me more…

Where does common law come from?

U.S. common law finds its origins in England, during the medieval era. It was developed mainly after the Norman Conquest and strengthened under the reign of King Henry II during the 12th century. The term "common law" dates from this period.

Initially, the King's Court was the only Court in the country at that time and was judging cases based on procedural remedies. This practice, based on remedies, led later on to the modern law system built on rights as the primary element. Back then, the church played an important role in justice matters. Henry II of England wanted to put in place a unique system to judge the legal issues and created the secular tribunals. Judges of these tribunals followed each other's decisions, and the "common" unified law was born. Moreover, from then on, the church and the state were to have their own legal systems and separate courts.

During these early stages, the customs and traditions were the foundation of the precedent established by the courts. When dealing with justice matters, the monarchy made use of formal orders named "writs." But this type of rule was not comprehensive enough to cover all situations that popped up. So, the courts of equity were charged with hearing the complaints and applying remedies issued from equitable principles. Along the way, these court decisions were collected and published and used by other judges for similar facts and cases. Thus, the common law was generated and developed mostly by judges.

In the United States, the common law appeared during the colonial era, when the colonists brought with them their law system. After the American Revolution, the new states embraced their own version of common law, which is a different set of judicial rules from the federal law.

What are some examples of common law?

Some well known common law examples are connected to common-law marriage, the common law concept related to the confidentiality of the doctor-patient relationship, and common-law copyright.

The concept of common-law marriage acknowledges similar rights as those that have a marriage license to couples that are not officially married, if several conditions are met.

Not all states recognize common law marriage. In the United States, for example, it is valid in the District of Columbia and 10 other States.

In U.S. states that allow common-law marriage, the needed conditions are more or less the same. These conditions are:

  • Members of the couple live together for an extended period of time
  • Both members have the legal right to marry
  • Neither of them is married to another person
  • They present themselves in front of friends and family as a married couple
  • They have joint bank accounts/credit cards

Another familiar common law example is the one referring to patient-doctor confidentiality. The legal concept means that the information related to the patient's health state, patient's treatment, medical opinion, or medical records is private and secret. The doctor has no right to reveal such details about his patient to other persons.

Common law copyright was the way small businesses could protect their products, art, books, music, digital assets from fraudulent use before the Copyright Act of 1976. It comprised the judicial rulings that protected the original works when there was no official legislation.

What is the difference between common law and civil law?

Common law and civil law are the basis of the two most used law systems across the globe. The common law system relies on previous judicial decisions made by law courts in similar cases (aka precedent or stare decisis) and statutory law. The civil law system relies primarily on legal codes and statutes (i.e. civil code, penal code, fiscal code) that are updated periodically. Both law systems have common law, codes, and statutes, but their importance inside the system is different.

Common law has its origin in the English monarchy legal tradition, while the civil law has its background in the Roman law tradition. Common law systems are considered adversarial, and the judge moderates the process between parties. Civil law systems are considered investigatory, and the judge has the principal role in proceedings, as they establish facts, bring charges, examine the witnesses, and apply remedies. Lawyers' role in common law jurisdictions is more relevant than in civil law legal systems as they typically hold presentations, bring arguments, and investigate witnesses.

Examples of common law countries are:

  • United Kingdom
  • United States
  • Canada
  • India

Examples of civil law jurisdictions are:

  • France
  • Germany
  • Spain
  • Japan

What state in the U.S. does not practice common law?

Louisiana is the only jurisdiction in the United States that has a civil law system.

The reason for this can be traced to the unique history of Louisiana as a former colony of France and Spain, two civil law system countries. For example, the private law (the area that deals with the relations between individuals) in Louisiana is built on the civil laws of France and Spain, but Louisiana's criminal law has significant influences from the U.S. Common law.

Ready to start investing?
Sign up for Robinhood and get your first stock on us.Certain limitations apply

The free stock offer is available to new users only, subject to the terms and conditions at rbnhd.co/freestock. Free stock chosen randomly from the program’s inventory. Securities trading is offered through Robinhood Financial LLC.


Related Articles

You May Also Like

The 3-minute newsletter with fresh takes on the financial news you need to start your day.
The 3-minute newsletter with fresh takes on the financial news you need to start your day.

© 2021 Robinhood. All rights reserved.

This information is educational, and is not an offer to sell or a solicitation of an offer to buy any security. This information is not a recommendation to buy, hold, or sell an investment or financial product, or take any action. This information is neither individualized nor a research report, and must not serve as the basis for any investment decision. All investments involve risk, including the possible loss of capital. Past performance does not guarantee future results or returns. Before making decisions with legal, tax, or accounting effects, you should consult appropriate professionals. Information is from sources deemed reliable on the date of publication, but Robinhood does not guarantee its accuracy.

Robinhood Financial LLC provides brokerage services. Robinhood Securities, LLC, provides brokerage clearing services. Robinhood Crypto, LLC provides crypto currency trading. Robinhood U.K. Ltd (RHUK) provides brokerage services in the United Kingdom. All are subsidiaries of Robinhood Markets, Inc. ('Robinhood').