The textual canons are about language. A second family, the substantive canons, are about values the legal system protects. They tell a court which way to lean when a statute is unclear.
Key idea
Substantive canons reflect legal values: the rule of lenity (read unclear criminal laws in the defendant's favor), constitutional avoidance (prefer a fair reading that avoids serious constitutional doubts) and clear-statement rules (Congress must speak clearly to do certain things, such as override a state's sovereign immunity).
| Canon | What it protects | When it applies |
|---|---|---|
| Rule of lenity | fair notice; the legislature's power to define crimes | a criminal statute is still ambiguous after the ordinary tools are used |
| Constitutional avoidance | the Constitution; respect for Congress | one fair reading raises serious constitutional doubts and another does not |
| Clear-statement rules | federalism and other structural values | a reading would alter the federal-state balance, abrogate state immunity, apply a law retroactively or outside the country |
| Major questions doctrine | Congress's role in deciding major policy | an agency claims power of vast economic or political significance from vague words |
Why it works
The rule of lenity is old: in United States v. Wiltberger (1820) Chief Justice Marshall wrote that the power of punishment is vested in the legislature, not the courts, so courts should not stretch criminal laws to cover cases the words do not clearly reach. Avoidance assumes Congress means to act within the Constitution and lets courts avoid striking laws down. Clear-statement rules protect structural arrangements that Congress should not be presumed to disturb by accident. The major questions doctrine, rooted in FDA v. Brown & Williamson (2000), requires clear authorization when an agency claims power over a question of vast economic and political significance. Supporters say it keeps major policy choices with the elected Congress; critics say it is a judge-made limit not found in the text and can block agencies from using powers Congress gave in broad terms.
Worked example: Lenity
A statute increases the sentence for anyone who "uses a weapon" during a robbery. Courts disagree whether showing a gun without firing it is "use." After text, context and history, the question is still evenly balanced. What does lenity suggest?
- Lenity applies only to real ambiguity that remains after the ordinary tools.
- Here it remains.
- Choose the narrower reading, favoring the defendant.
Answer: Read "uses" narrowly; the enhancement does not apply.
Worked example: Avoidance
A statute lets officials refuse permits to groups that are "disruptive." Read broadly, it could punish unpopular speech, raising serious First Amendment doubts. Read narrowly, it covers only physical disruption of traffic. What does the avoidance canon suggest?
- Two fair readings exist.
- The broad one raises serious constitutional doubts; the narrow one does not.
- Adopt the narrow one, without deciding whether the broad one would be unconstitutional.
Answer: The narrow reading (physical disruption).
Common mistake
Applying lenity whenever a criminal statute is hard to read. Courts generally use it only when real ambiguity remains after the other tools of interpretation (text, structure, context and, for some judges, history). Check: have you tried the ordinary tools first? Lenity is a tie-breaker, not a starting point.
This is an educational course, not legal advice.