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Every legal argument you'll encounter traces back to a source of law. Understanding where law comes from is the foundation for determining which rules apply, which authority wins when laws conflict, and how legal change actually happens. You're being tested on your ability to identify hierarchy, origin, and function for each source.
Sources of law form a layered system where some sources trump others, some fill gaps left by others, and some only exist because another source authorized them. Don't just memorize definitions. Know what makes each source legitimate, who creates it, and where it falls in the pecking order. That's what separates a surface-level answer from one that shows real legal reasoning.
These sources represent law that has been formally written down and enacted through official governmental processes. The key principle here is hierarchy: when these sources conflict, the higher-ranked source wins.
The U.S. Constitution is the supreme law of the land. Every other law, at every level of government, must conform to it or be struck down as invalid. State constitutions play the same role within their states, though they too must comply with the federal Constitution.
Constitutions serve two core functions:
Because constitutions are meant to be enduring, they're deliberately hard to change. Amending the U.S. Constitution requires a two-thirds vote in both chambers of Congress and ratification by three-fourths of state legislatures.
Statutes are laws enacted by legislatures at the federal, state, or local level. They create specific rules governing conduct in society. Their legitimacy comes from the democratic process: elected representatives debate, vote on, and pass proposed legislation through formal procedures.
Unlike constitutional provisions, statutes are relatively flexible. The same legislative body that passed a statute can amend or repeal it through ordinary legislative procedures. This makes statutes the most common vehicle for addressing new social problems or changing policy.
Ordinances are municipal-level laws enacted by cities, counties, or other local government entities. They address community-specific needs like zoning, noise regulations, parking, and local business licensing.
Their jurisdiction is limited. Ordinances must comply with both state and federal law. A city can add specificity to state requirements, but it cannot contradict them.
Compare: Constitutions vs. Statutes: both are enacted by governmental bodies, but constitutions are harder to change and trump statutes when they conflict. If a question asks about judicial review, remember that courts measure statutes against constitutional requirements.
Not all law comes from legislatures. Courts create law through their decisions, either by interpreting existing sources or by developing legal principles where no statute exists.
When judges decide cases, their written opinions become case law. The doctrine of stare decisis (Latin for "to stand by things decided") requires courts to follow prior rulings in cases with similar facts. This precedent system creates predictability: parties can look at how courts ruled before and anticipate how they'll rule again.
Case law is evolutionary by nature. Judges apply established principles to new circumstances, and over time, the law adapts as societal values shift. A court can also distinguish or overturn prior precedent, though this happens cautiously.
Equity developed historically as a separate body of fairness-based remedies for situations where common law courts couldn't provide adequate relief. If money alone wouldn't fix the problem, equity stepped in.
Compare: Common Law vs. Equity: both are judge-made, but common law typically awards money damages while equity provides non-monetary remedies like injunctions. Know this distinction for questions about available remedies.
The executive branch doesn't just enforce law; it also creates it. These sources derive their authority from constitutional or statutory grants of power and represent law made outside the legislative process.
Executive orders are directives issued by a president or governor that manage government operations and implement policy without requiring legislative action. They carry the force of law within the executive branch.
That said, executive orders aren't unchecked. Courts can strike them down if they exceed constitutional authority, and legislatures can pass laws that override them. Presidents frequently use executive orders to respond quickly to crises or set administrative priorities.
When Congress passes a statute, it often writes the law broadly and delegates the details to a specialized administrative agency. The agency then creates regulations that provide specific implementation guidance.
Agencies only have the power that Congress or a state legislature has granted them. This is called delegated authority. And the process for creating regulations is more formal than you might expect:
This is the notice-and-comment process, and it's a frequent exam topic.
Compare: Executive Orders vs. Regulations: both come from the executive branch, but executive orders come directly from the chief executive while regulations come from administrative agencies. Regulations typically go through the more formal notice-and-comment process.
Some legal sources extend beyond domestic governmental action. These sources bind nations to each other or reflect practices so widespread they've become legally obligatory.
Treaties are formal written agreements between sovereign nations that create binding legal obligations. In the U.S., the President negotiates treaties, but the Senate must approve them by a two-thirds vote before they take effect domestically.
Once ratified, treaties hold equal standing with federal statutes under the Supremacy Clause. If a treaty and a statute conflict, the one enacted later in time generally controls.
Not all international law is written down. Customary international law consists of practices that have become legally binding through consistent, widespread observance over time. Two elements must be present: states must follow the practice regularly, and they must do so out of a sense of legal obligation (not just convenience or habit).
Customary law is especially significant in human rights and humanitarian contexts, where it can bind nations even without a formal treaty. It fills gaps where no written agreement exists.
Compare: Treaties vs. Customary Law: both govern international relations, but treaties are written and require formal consent while customary law emerges organically from state practice. Treaties provide clearer rules; customary law fills gaps where no treaty exists.
These sources help lawyers and judges understand the law but don't create binding legal rules themselves. The distinction between primary and secondary sources is fundamental to legal research.
Secondary sources are analytical resources like treatises, law review articles, Restatements of the Law, and legal encyclopedias. They explain, interpret, and organize primary sources.
The critical point: secondary sources are persuasive but not binding. A court might find a law review article's reasoning helpful, but it's never required to follow it. For research purposes, secondary sources are valuable starting points that help you identify relevant primary authority and understand complex legal doctrines.
| Concept | Best Examples |
|---|---|
| Highest authority (supremacy) | Constitutions |
| Legislative enactments | Statutes, Local Ordinances |
| Judge-made law | Case Law/Common Law, Equity |
| Executive branch sources | Executive Orders, Regulations |
| International sources | Treaties, Customary Law |
| Interpretive tools (non-binding) | Secondary Sources |
| Requires formal ratification | Treaties, Constitutions (amendments) |
| Subject to notice-and-comment | Regulations |
If a state statute conflicts with a provision in the state constitution, which source controls and why?
Both case law and equity are judge-made. What distinguishes the types of remedies each traditionally provides?
Compare executive orders and administrative regulations: How do their creation processes differ, and what gives each the force of law?
A legal encyclopedia provides an excellent explanation of contract law principles. Can a court cite this as binding authority? Explain the distinction between primary and secondary sources.
Treaties and customary international law both govern relations between nations. If you were arguing that a nation violated international human rights standards but no treaty applied, which source would you rely on and why?