Law Legal ReasoningWhat Is Law? Sources and Systems
Sage, a calm robed mentor, stands before a tall library shelf labeling four glowing law books while a map of legal traditions hangs nearby
- Define law as a system of binding rules enforced by public authority
- Identify the four main sources of law: constitutions, statutes, regulations, and case law
- Compare how common law and civil law systems treat past court decisions differently
- Explain why a constitution outranks a statute in jurisdictions that recognize constitutional supremacy
- Classify a given rule by the source of law it comes from
Key terms
- Binding rule
- A rule a court can enforce, not merely suggest, made and applied by public authority.
- Constitution
- In many countries the highest law, which sets up government and limits its power.
- Statute
- A law passed by a legislature such as a congress or parliament.
- Regulation
- A detailed rule written by a government agency to carry out a statute.
- Case law
- The body of rulings judges produce when they decide real disputes.
The Four Sources of Law
Law draws from four distinct sources arranged in a hierarchy in many countries. A constitution sits highest where it exists, founding the government and limiting its power so that other law must conform — though systems like the United Kingdom's parliamentary sovereignty arrange authority differently. Statutes are enacted by legislatures, regulations are written by agencies to implement those statutes, and case law accumulates from judges deciding disputes. Identifying which source a rule comes from clarifies both its authority and how it can be changed or challenged.
Common Law Versus Civil Law
Countries organize these sources into recognizable systems. In common law systems such as the United States and England, prior court decisions act as precedent that later judges are formally expected to follow under stare decisis, so case law carries great weight. In civil law systems such as France and Germany, comprehensive written codes are the primary authority and judges are not formally bound by earlier rulings — though high-court decisions still carry persuasive weight in practice. The contrast lies chiefly in how each tradition treats the binding force of past decisions.
Worked examples
Classify an agency's airbag safety standard by source.
- Issue: Which source of law is a detailed agency standard specifying how businesses must comply with a statute?
- Rule: Regulations are detailed rules that government agencies write to carry out statutes.
- Application: The airbag standard is issued by an agency to implement a broader statutory requirement, not by a legislature, court, or constitutional convention.
- Conclusion: It is a regulation.
Answer: It is a regulation — an agency rule implementing a statute.
Resolve a statute that conflicts with a supreme constitution.
- Issue: When a new statute conflicts with a supreme written constitution, which controls?
- Rule: A constitution sits above statutes in the legal hierarchy, so conflicting lower-tier law must yield.
- Application: Although newer laws can override older ones of equal rank, that principle does not cross hierarchy levels; the statute is below the constitution.
Answer: The constitution controls — a conflicting statute must give way regardless of which is newer.
Activity
Match each rule or document to the source of law it belongs to
Practice
Match four rules or documents to the source of law each belongs to: constitution, statute, regulation, or case law.
Explain how a common law and a civil law system would each treat a prior high-court decision.
Common mistakes to avoid
- Common and civil law treat precedent the sameCommon law formally binds later courts through stare decisis, while civil law centers on written codes and treats prior rulings as merely persuasive.
- A newer statute always beats an older constitutionThe lex posterior principle applies only within the same rank, so a constitution still outranks a later conflicting statute in the hierarchy.
Check your understanding
Which best defines 'law' as used in this lesson?
An agency writes a detailed rule spelling out exactly how businesses must follow a statute. What source of law is this?
In which system are past court decisions treated as formal precedent that later judges are expected to follow?
In a country with a supreme written constitution, a new statute conflicts with the constitution. Which controls?
Recap
Law is a system of binding rules from four sources — constitutions, statutes, regulations, and case law — organized into common law systems that follow precedent through stare decisis and civil law systems built mainly on written codes.
Reflect
Which source of law do you think most directly shapes everyday life, and why?