What Is the Difference Between Civil Law and Common Law? Legal Systems Explained
Civil law and common law are two distinct legal systems that differ fundamentally in how they create, interpret, and apply law. Common law systems—used in 49 U.S. states—rely on judicial precedent and case law to establish legal principles, while civil law systems—used in Louisiana and some U.S. territories—rely on comprehensive written legal codes and statutes with less emphasis on precedent.
According to legal scholars, approximately 150 countries worldwide use civil law systems descended from Roman law, while common law systems originating in England govern about 80 countries including most of the United States. Understanding which system governs your state affects how courts interpret contracts, resolve disputes, and determine your legal rights.
Historical Origins Shape Modern Legal Systems
Common Law Evolved Through English Judicial Tradition
Common law—a legal system based on judicial precedent and case law originating in England—developed after the Norman Conquest of 1066 when English kings established royal courts to create uniform law across the kingdom. Judges traveled circuits resolving disputes, and their decisions became precedents that guided future cases.
This judge-made law emphasized consistency through the doctrine of stare decisis—Latin for “to stand by things decided”—which requires courts to follow prior decisions on similar legal questions. Over centuries, common law spread to English colonies including the original thirteen American colonies, establishing the foundation for most U.S. state legal systems.
Civil Law Descended from Roman Legal Codes
Civil law systems trace their origins to ancient Roman law, particularly the Corpus Juris Civilis compiled under Emperor Justinian in the 6th century. This comprehensive legal code established the principle that law should be systematically organized in written statutes rather than developed through judicial decisions.
The Napoleonic Code of 1804 modernized civil law principles and influenced legal systems across continental Europe, Latin America, and Louisiana. When Louisiana joined the United States in 1803, it retained its French and Spanish civil law heritage, making it the only U.S. state with a comprehensive civil law system based on the Louisiana Civil Code.
Core Structural Differences Between the Two Systems
The Role of Precedent Distinguishes Each System
In common law jurisdictions, precedent serves as binding authority—prior court decisions must be followed by lower courts within the same jurisdiction. When a state supreme court interprets a statute or establishes a legal principle, that interpretation binds all lower courts in the state until the supreme court overrules its own precedent or the legislature changes the statute.
The Sierra Mist trademark dispute illustrates how common law trademark rights allow companies to retain rights over names through continued commercial use, even if formal registration lapses—a principle developed through decades of judicial precedent rather than comprehensive statutory codes.
Civil law systems treat precedent differently. Judges in civil law jurisdictions apply written codes and statutes directly to each case without being bound by prior judicial decisions. While civil law judges may consider prior decisions persuasive, they have no obligation to follow them—each case is decided based on the code’s provisions rather than accumulated case law.
Judges Play Different Roles in Each System
Common law judges interpret statutes, fill gaps in legislation, and create legal principles through written opinions. These judicial opinions explain the court’s reasoning and establish precedents that guide future cases. American common law judges exercise significant discretion in interpreting ambiguous statutes and developing legal doctrines through case-by-case analysis.
Civil law judges function primarily as code interpreters rather than law creators. They apply codified legal provisions to specific facts without the expectation that their decisions will bind future courts. Civil law judicial opinions tend to be shorter and less detailed than common law opinions because they don’t serve as precedential authority.
Written Codes Versus Case Law as Primary Sources
Civil law systems organize law into comprehensive codes covering specific legal areas—civil procedure, criminal law, commercial transactions, family law. The Louisiana Civil Code, for example, contains systematic provisions governing contracts, property, obligations, and personal relationships.
Common law systems rely primarily on accumulated judicial decisions (case law) alongside statutes enacted by legislatures. When courts interpret statutes in common law jurisdictions, those interpretations become part of the law itself through precedent. This creates layered legal authority combining statutory text with judicial glosses developed over time.
Practical Implications for Dispute Resolution
Contract Interpretation Differs Between Systems
When courts interpret contracts, the legal system governing the jurisdiction significantly affects the outcome. Common law courts examine prior judicial decisions interpreting similar contract language, apply established principles of contract interpretation developed through precedent, and create new precedents when facing novel contract issues.
Civil law courts apply code provisions governing contracts directly to the dispute without extensive reliance on prior judicial interpretations. Louisiana courts, for instance, apply Louisiana Civil Code articles on contracts, obligations, and interpretation rather than looking primarily to prior Louisiana court decisions.
Statutory Interpretation Follows Different Approaches
Common law courts use various interpretive techniques developed through precedent—textualism, purposivism, legislative history analysis—and their interpretations become binding precedent for future cases involving the same statute. This means statutory meaning evolves through accumulated judicial interpretations.
Civil law courts interpret codes more directly, focusing on the code’s systematic structure and internal logic rather than external judicial glosses. Because prior decisions aren’t binding, each civil law judge interprets the code independently, though patterns of interpretation may develop over time.
What Americans Get Wrong About Legal Systems
Assuming All U.S. States Use the Same Framework
The most common misconception: all U.S. states operate under identical legal systems. In reality, Louisiana’s civil law heritage creates fundamental differences in how courts interpret law, how attorneys practice, and how legal rights are determined compared to common law states.
This distinction matters for individuals relocating to Louisiana, businesses operating across state lines, and anyone signing contracts governed by Louisiana law. Legal principles taken for granted in common law states may not apply under Louisiana’s civil law framework.
Confusing Civil Law with Civil Litigation
Many people confuse “civil law” as a legal system with “civil litigation”—lawsuits between private parties rather than criminal prosecutions. These are completely different concepts. Civil law systems govern how all law (both civil and criminal) is structured and interpreted, while civil litigation refers to non-criminal lawsuits in any legal system.
Understanding this distinction helps avoid confusion when researching legal topics or discussing legal rights in different contexts.
Believing Precedent Never Matters in Civil Law
While civil law systems don’t treat precedent as binding authority, civil law judges still consider prior decisions persuasive. In practice, patterns of interpretation develop even in civil law jurisdictions, creating predictability despite the theoretical absence of binding precedent.
Louisiana courts, for example, regularly cite prior decisions as persuasive authority when interpreting the Louisiana Civil Code, even though those decisions don’t technically bind future courts.
Understanding Your State’s Legal System
Identify Which System Governs Your State
Most U.S. states use common law systems inherited from English legal tradition. Louisiana uses a civil law system based on the Louisiana Civil Code. Puerto Rico and some U.S. territories also use civil law systems influenced by Spanish legal tradition.
Knowing your state’s legal system helps you understand how courts will interpret contracts you sign, what legal precedents may apply to disputes, and how judges approach statutory interpretation in your jurisdiction.
Recognize Implications for Legal Transactions
When signing contracts, understand that common law courts will interpret ambiguous terms by looking to prior judicial decisions, while civil law courts apply code provisions more directly. This affects contract drafting, dispute resolution, and enforcement strategies.
Business owners operating across multiple states should recognize that Louisiana’s civil law framework may require different contractual language, legal analysis, and litigation strategies compared to common law states.
Consult Attorneys Familiar with Your Jurisdiction’s System
If you’re involved in a legal dispute, signing a major contract, or relocating to a different state, consult an attorney familiar with that jurisdiction’s legal system. Attorneys practicing in Louisiana must understand both civil law principles and how Louisiana law interacts with federal common law, while attorneys in common law states focus primarily on precedent and case law analysis.
State bar associations can help you find attorneys with expertise in your jurisdiction’s legal system.
Frequently Asked Questions
What Is the Difference Between Common Law and Civil Law?
Common law relies on judicial precedent and case law as primary legal sources—courts follow prior decisions through the doctrine of stare decisis. Civil law relies on comprehensive written codes and statutes—judges apply the code to specific cases without being bound by prior decisions. Common law originated in England; civil law descended from Roman law and the Napoleonic Code.
Which U.S. States Use Civil Law Versus Common Law?
Forty-nine U.S. states use common law systems inherited from English legal tradition. Louisiana uses a civil law system based on the Louisiana Civil Code, reflecting its French and Spanish colonial heritage. Puerto Rico and some U.S. territories also use civil law systems, while most U.S. jurisdictions operate under common law frameworks.
How Does Precedent Work in Common Law Systems?
Precedent operates through stare decisis—courts must follow prior decisions from higher courts in the same jurisdiction. When a state supreme court interprets a statute or establishes a legal principle, lower courts in that state must follow that interpretation. Precedent creates consistency and predictability, allowing lawyers and individuals to anticipate how courts will rule on similar issues.
Why Does the United States Have Both Civil Law and Common Law Systems?
The United States inherited common law from England through colonial legal traditions, but Louisiana retained its French and Spanish civil law heritage when it joined the United States in 1803. The U.S. Constitution allows states to maintain their own legal systems, so Louisiana preserved its civil law framework while most states adopted common law. This creates legal diversity within the federal system.
How Does the Legal System Affect How Courts Interpret Contracts?
Common law courts interpret contracts by examining prior judicial decisions on similar language, applying established precedential principles of contract interpretation, and creating new precedents when facing novel issues. Civil law courts apply code provisions governing contracts directly without extensive reliance on prior judicial interpretations. This means identical contract language may be interpreted differently depending on whether the governing law is common law or civil law.
Do I Need to Understand Civil Law and Common Law to Protect My Legal Rights?
Understanding your state’s legal system helps you anticipate how courts will interpret contracts, what legal precedents may apply to disputes, and how judges approach legal questions in your jurisdiction. While you don’t need expert knowledge, recognizing whether you live in a common law or civil law state affects how you should approach legal transactions and disputes. Consult an attorney when legal questions arise to ensure you understand how your jurisdiction’s legal system affects your specific situation.
Last Updated: January 20, 2026
Disclaimer: This article is for informational purposes only and does not constitute legal advice; consult an attorney for guidance on your specific situation or questions about how civil law or common law principles apply to your case.
Take Action: Identify whether your state uses a common law or civil law system, understand how that framework affects contract interpretation and dispute resolution in your jurisdiction, recognize the role of precedent and judicial interpretation in your state’s legal system, and consult an attorney when facing legal questions to ensure you understand how your state’s legal framework applies to your specific situation.
Stay informed, stay protected. — AllAboutLawyer.com
Sources and Citations
- Louisiana Civil Code (www.legis.la.gov)
- Uniform Power of Attorney Act (§110) – example of common law statutory framework
- Louisiana Supreme Court official website (www.lasc.org)
- American Bar Association, “Civil Law and Common Law Systems” comparative analysis
- Harvard Law School, “Introduction to Civil Law Legal Systems”
- Yale Law School, “The Common Law Tradition”
- National Conference of State Legislatures, “State Legal Systems Overview”
- Federal Judicial Center, “Legal Systems in U.S. Jurisdictions”
About the Author
Sarah Klein, JD, is a licensed attorney and legal content strategist with over 12 years of experience across civil, criminal, family, and regulatory law. At All About Lawyer, she covers a wide range of legal topics — from high-profile lawsuits and courtroom stories to state traffic laws and everyday legal questions — all with a focus on accuracy, clarity, and public understanding.
Her writing blends real legal insight with plain-English explanations, helping readers stay informed and legally aware.
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