Mastering Federal Statutory Interpretation Guidelines for Legal Clarity
How often do you encounter a federal statute that seems unclear, leaving you unsure of its true meaning? Federal statutory interpretation guidelines provide a structured, text-based approach to resolve that ambiguity, focusing on the statute’s plain language, context, and purpose. By methodically applying canons of construction and analyzing legislative intent, these guidelines help you achieve a consistent and defensible legal outcome. Use them to anchor your analysis in the law’s own words, ensuring your conclusions are both logical and faithful to the statute’s design.
Core Canons of Construction
The core canons of construction within federal statutory interpretation are textualist tools used to resolve ambiguity by analyzing a statute’s words. The plain meaning rule dictates that if the language is unambiguous, the inquiry ends. The rule against surplusage presumes every word has effect, so an interpretation rendering a term superfluous is avoided. Ejusdem generis limits general terms following specific ones to items of the same class. Noscitur a sociis derives meaning from surrounding words. Q: When does the canon of constitutional avoidance apply? A: It directs courts to adopt a permissible interpretation of a federal statute that avoids serious constitutional doubts, but only if the statute is genuinely ambiguous and the alternative construction is reasonable.
The Plain Meaning Rule and Its Limits
The Plain Meaning Rule is the starting point: if a federal statute’s language is clear, you apply it as written. Its limits kick in when the text produces absurd results or internal contradictions. Courts then look beyond the dictionary to resolve ambiguity. Absurdity doctrine exceptions often save a statute from its own words. For example, a plain reading might contradict Congress’s clear intent, forcing judges to check purpose or context. This isn’t guesswork—it’s a structured fallback. Here’s the sequence:
- Read the statute’s plain text.
- Check if that reading leads to an absurd or impractical outcome.
- If it does, consult legislative context, structure, or broader scheme.
- Apply a reasonable interpretation that avoids absurdity.
These limits keep plain meaning from becoming a trap.
Textualism Versus Purposivism in Practice
In federal statutory interpretation, textualism and purposivism diverge sharply in practice. Textualists prioritize the ordinary public meaning of the statute’s words at enactment, often relying on dictionaries and grammatical structure, while purposivists seek the broader legislative intent or problem the law was designed to fix. This tension surfaces most acutely in ambiguous provisions. A textualist might reject extraneous committee reports as unreliable, whereas a purposivist would consult them to resolve ambiguity. Both approaches, however, must grapple with canons like the whole act rule, which can align or conflict with either method.
How does this affect a practitioner’s argument? If the statutory text yields a clear meaning, textualism largely prevails; purposivism becomes relevant only when that meaning produces absurd or internally inconsistent results, forcing a choice between fidelity to words or perceived purpose.
Noscitur a Sociis: Associative Word Interpretation
Noscitur a sociis, Latin for “it is known by its associates,” directs courts to interpret ambiguous words in a federal statute by examining the neighboring terms. Under this canon, a term’s meaning is narrowed or clarified through the company it keeps—the accompanying words in a phrase or list. For example, if a statute lists “cars, trucks, and vehicles,” the term “vehicles” is likely restricted to motorized road transport, not all conveyances. This prevents broad, unintended definitions by anchoring interpretation to the context of the surrounding text.
- Apply it when a word is ambiguous among multiple plausible meanings.
- Identify the shared characteristics of the grouped words to limit the disputed term.
- Use it to avoid interpretations that would make adjacent legislative terms redundant.
- Pair it with other canons, like ejusdem generis, for precise statutory reading.
Ejusdem Generis: General Terms Following Specifics
Ejusdem generis is a federal statutory interpretation canon applied when a general term follows a list of specific items. Under this www.harvardjol.com rule, the general term is construed to include only things of the same kind, class, or nature as those specifically enumerated. For example, if a statute lists “cars, trucks, and motorcycles” and then prohibits “other vehicles,” the general term “vehicles” would likely exclude airplanes or boats. Courts must first identify the common characteristic tying the specific terms together to define the class. This avoids expansive readings of catch-all clauses, ensuring the statute’s scope remains anchored to its enumerated examples.
Ejusdem Generis limits a general term to items sharing the same class as the preceding specific terms.
Expressio Unius Est Exclusio Alterius: Express Mention and Implied Exclusion
When applying expressio unius exclusio alterius in federal statutory interpretation, the idea is straightforward: if a law explicitly lists certain items, it implies that anything not on that list is intentionally left out. For example, if a statute says “this rule applies to cars and trucks,” it likely does not cover bicycles or scooters. This canon helps you pinpoint the statute’s boundaries by focusing on what is specifically mentioned. It’s a practical tool for avoiding over-expanding a law’s reach, but remember courts often pair it with context to ensure the exclusion was truly intended.
- Focus on exact words: only items the statute names are covered.
- Check legislative intent: implied exclusion can be overridden if other evidence suggests a broader scope.
- Use alongside other canons, like noscitur a sociis, to avoid misreading the list.
Tools for Resolving Ambiguity
When a statute’s language splits open like a cracked bell, Tools for Resolving Ambiguity become the interpreter’s hammer and anvil. The whole act rule sews the ambiguous clause back into the fabric of the surrounding sections, reading each word as part of a coherent body. If that stitch fails, the purpose clause or findings section of the federal statute itself glows like a lantern, revealing what Congress meant to mend. A federal judge once told me that the presumption against absurd results is her first reflex: if one reading would make a program collapse under its own weight, the other reading must be right. These aren’t academic toys—they’re the actual chisels a lawyer or analyst uses to carve meaning out of a statutory crack.
Statutory Context and the Whole-Act Rule
When a federal law’s wording feels fuzzy, judges don’t just stare at one sentence. They apply the Statutory Context and the Whole-Act Rule to see the big picture. The core idea is that a single phrase gains meaning from the entire statute around it. To figure out an ambiguous term, you follow a clear sequence:
- Read the ambiguous section in full, not in isolation.
- Scan the whole act for definitions, exceptions, or cross-references that clarify the term.
- Check the act’s structure—titles, headings, or how other sections use the same word—since consistency is presumed.
This rule stops you from pulling a phrase out of context, ensuring every part of the law works together practically.
Harmonizing Conflicting Provisions
When a federal statute contains two provisions that directly contradict each other, the interpreter’s first duty is to attempt harmonizing conflicting provisions to give effect to the entire text. This requires reading the sections in context to see if one serves as an exception, a general rule, or a temporal limitation on the other. For example, a broad prohibition may be reconciled with a narrower allowance by treating the latter as a carve-out. If no logical reconciliation is possible, the more specific provision typically governs the general one. This method avoids declaring an ambiguity outright until all structural connections are exhausted.
Q: How do you decide which provision takes priority when harmonizing fails?
A: When literal harmonization is impossible, the interpreter applies the rule that the later-enacted provision repeals the earlier one, or the more specific provision controls the general.
Presumption Against Absurd Results
The Presumption Against Absurd Results is a core tool for resolving ambiguity in federal statutory interpretation. It directs courts to choose a reading that avoids an outcome Congress could not have plausibly intended—even if the plain text seems to point elsewhere. For example, if a statute’s literal words would require a driver to stop for a red light at a deserted intersection at 3 AM, this presumption lets a judge read in a commonsense exception for safety. Common sense is your guide here.
Q: Can this presumption overturn clear statutory language?
A: Rarely—it applies only when the text is genuinely ambiguous and the absurd result is obvious, not just inconvenient.
Rule of Lenity in Criminal Statutes
The Rule of Lenity directs courts to resolve genuine ambiguity in a criminal statute in favor of the defendant. It applies only after other interpretive tools—text, structure, and legislative history—fail to clarify Congress’s intent. This principle safeguards against arbitrary punishment by ensuring that no one is convicted under a law whose prohibitions are unclear. Federal guidelines treat it as a last-resort canon, not a primary interpretive method. Its practical effect is narrow but decisive: when a statute remains irreducibly ambiguous, the defendant receives the benefit of the doubt.
The Rule of Lenity resolves irremediable ambiguity in criminal statutes by deferring to the interpretation most favorable to the accused.
Presumption Against Retroactive Application
The presumption against retroactive application operates as a critical tiebreaker in federal statutory interpretation. When ambiguity arises, courts assume Congress intends laws to apply only prospectively—affecting future conduct, not past events. This rule forces interpreters to demand explicit, clear language if a statute purportedly reaches backward. Practically, this presumption protects reliance interests, ensuring parties aren’t blindsided by new legal consequences for completed actions. To overcome it, a statute must plainly express retroactive effect or a contrary intent must be unavoidable from the text. This tool prevents judicial speculation about hidden temporal scope, grounding ambiguous timing questions in textual clarity alone.
Extrinsic Aids in Interpretation
In federal statutory interpretation, extrinsic aids become essential when a statute’s plain meaning is ambiguous or leads to absurd results. Under federal guidelines, courts consult legislative history—including committee reports, floor statements, and hearing testimony—to discern congressional intent. These aids also encompass administrative interpretations from the enforcing agency, which are granted deference when consistent and reasonable. Always prioritize the statutory text first, as extrinsic evidence supplements, never replaces, clear language. A common question: Q: When are extrinsic aids most persuasive under federal guidelines? A: When they demonstrate a clear, bicameral consensus on the specific interpretive issue, such as a conference committee report explaining a disputed term. Practical use demands verifying that the aid directly addresses the provision at hand and aligns with the overall statutory structure, avoiding cherry-picked remarks from lone legislators.
Legislative History: Committee Reports and Floor Statements
Committee reports, particularly from conference committees, are often considered the most authoritative legislative history because they represent the final, agreed-upon explanation of a bill’s purpose. Floor statements, while less reliable due to potential strategic posturing, can provide context for ambiguous terms if made by the bill’s sponsor. The primary sequence for evaluating these documents involves:
- Prioritizing conference reports over standing committee or subcommittee reports.
- Consulting floor statements only where the committee report remains ambiguous.
- Giving less weight to statements made by non-sponsoring members, as they do not reflect the drafting legislature’s collective intent.
Agency Interpretations and the Chevron Doctrine
When a statute administered by a federal agency is ambiguous, courts apply the Chevron deference framework to determine whether the agency’s interpretation is permissible. Under this two-step analysis, the court first asks if Congress directly addressed the precise question—if so, the plain meaning controls. If the statute is silent or ambiguous, the court then defers to any reasonable agency interpretation, provided the agency acted within its delegated authority and offered a reasoned explanation. This doctrine makes agency guidance, such as informal rules or interpretive letters, a critical extrinsic aid for predicting statutory meaning in practice.
Agency interpretations carry binding weight under Chevron only when Congress left a gap for the agency to fill, and the agency’s reading is reasonable, not arbitrary.
Post-Enforcement Agency Guidance and Skidmore Deference
When courts look at Post-Enforcement Agency Guidance and Skidmore Deference, they consider how an agency interprets a statute after it has already enforced the law. Under this standard, a court gives respect to the agency’s interpretation based on its thoroughness, consistency, and reasoning—but it’s not binding like Chevron deference. For practical use, remember this sequence:
- Identify if the guidance was issued after enforcement actions began.
- Check if the agency’s reasoning is well-reasoned and persuasive.
- Apply Skidmore deference only if the interpretation is consistent over time.
This means your team should track how agencies explain their post-enforcement rulings, as those explanations can still influence a judge’s decision.
Dictionary Usage at the Time of Enactment
When federal courts engage in statutory interpretation, consulting dictionaries published at the time of a law’s enactment is a foundational extrinsic aid. This practice, known as contemporaneous dictionary usage, helps discern the ordinary public meaning of undefined terms as understood by Congress when it passed the statute. Courts prefer these period-specific definitions over modern dictionary entries to avoid anachronistic readings. For example, a term like “vehicle” in a 1920s act would be interpreted using a 1920s dictionary definition, not a current one. This approach anchors judicial analysis to the original semantic context, ensuring fidelity to Congressional intent and avoiding judicial updating of legislative language.
Preexisting Common Law and Judicial Precedent
Under federal statutory interpretation guidelines, preexisting common law and judicial precedent function as extrinsic aids when a statute’s text is ambiguous or silent. Courts presume Congress legislates against a backdrop of existing common law principles, meaning those principles inform the meaning of statutory terms unless explicitly displaced. Judicial precedent, particularly binding circuit or Supreme Court decisions, further shapes interpretation by resolving how similar statutory language was previously applied. This approach, known as the common law presumption, prevents courts from reading statutes in a vacuum, ensuring consistency between new federal laws and established legal doctrines. Practically, attorneys must research both the relevant common law history and any precedential gloss on the statute to anticipate interpretive outcomes.
Structural and Linguistic Analysis
Structural analysis under federal statutory interpretation guidelines demands you examine a statute’s internal architecture—its titles, sections, and punctuation—to deduce legislative intent from organizational patterns. Linguistic analysis requires applying canons of construction like noscitur a sociis (a word is known by its associates) to define ambiguous terms within their immediate textual context. Both methods are strictly subordinate to the statute’s plain meaning, which courts derive first from ordinary usage and grammatical structure. Practically, you must parse sentences for conjunctions and modifiers, then cross-reference definitions across the entire act, ensuring your interpretation aligns cohesively with the whole text, not isolated clauses. This dual approach prevents misuse of legislative history and keeps analysis grounded in the enacted words.
Punctuation, Grammar, and Syntax as Clues
In federal statutory interpretation, the precise placement of a comma or the choice of “and” versus “or” serves as a definitive clue to Congressional intent. Analysts scrutinize syntactic structure for legislative meaning, where a series qualifier (like the last antecedent rule) can dramatically alter the scope of a statute. Grammar reveals whether modifiers are restrictive or descriptive, while syntax dictates the logical relationship between clauses, preventing misinterpretation of complex, nested provisions. A missing preposition might turn a mandatory duty into a discretionary act.
Use of “Shall,” “May,” and “Must” in Drafting
In federal statutory interpretation, the precise use of modal verbs in legislative drafting dictates legal obligation versus discretion. “Shall” imposes a mandatory duty, leaving no room for agency judgment. “May” confers permissive authority, allowing the agency to act or not. “Must” is increasingly preferred to clarify a condition precedent or imperative requirement, reducing ambiguity that “shall” sometimes creates between a duty and a future event. Correct application of these terms ensures the text yields predictable legal effect, preventing courts from inferring unintended meanings or nullifying clear legislative intent.
Shall commands, may permits, and must clarifies—each verb directly controls the legal force of a statutory provision without guesswork.
Canon Against Surplusage: Giving Meaning to Every Word
The Canon Against Surplusage directs a court to avoid an interpretation that renders any statutory clause or word redundant. In federal statutory interpretation, this rule presumes Congress chose each term deliberately, with independent operative effect. Application follows a presumption of non-redundancy. A practical sequence includes:
- Identify all words in the disputed provision.
- Test each word for a distinct legal consequence; if one term adds nothing, the reading is suspect.
- Adopt only the construction giving every word meaning, unless context creates irreconcilable conflict.
This preserves structural coherence and prevents judicial subtraction of legislative language.
Referential and Incorporation by Reference Clauses
Incorporation by reference clauses allow a federal statute to legally adopt external documents (e.g., technical standards or agency rules) as binding text without reprinting them. In statutory interpretation, this creates a unique challenge: courts must determine whether the incorporated material is fixed at the time of enactment or evolves with future updates. Unlike mere referential clauses, which only point to external sources for guidance, incorporation by reference makes that external text authoritative. If the statute lacks explicit language about the incorporated document’s version, ambiguity arises that can shift interpretative weight from legislative intent to agency discretion. Practitioners must verify whether Congress used “as amended” or “as in effect on date” to lock or flex the reference.
| Clause Type | Interpretative Effect | Example Language |
| Referential | Non-binding guidance; court may ignore | “consult the guide” |
| Incorporation by Reference | Binding law; must be applied | “the standard is incorporated by reference” |
Title, Preamble, and Section Headings as Context
In federal statutory interpretation, the title, preamble, and section headings as context serve as immediate, structural clues to legislative intent. Courts use the title to frame the statute’s general scope, while the preamble often reveals the problem Congress aimed to solve. Section headings, though not law, guide readers to the subject matter of individual clauses. This layered context prevents misreading by anchoring ambiguous language within the statute’s own architecture. Analysts must examine these components together, as each refines the meaning of the operative text without rewriting it.
Title, preamble, and section headings establish the statutory framework, offering direct clues to legislative purpose and narrowing ambiguous language within the body of the law.
Constitutional and Federalism-Based Canons
Constitutional and federalism-based canons are interpretive rules courts use to avoid reading a federal statute in a way that creates serious constitutional problems. For example, the *clear statement rule* requires Congress to state explicitly if it intends to preempt state law, preserving state authority unless the federal text is unmistakable. Q: Why do these canons matter for you? A: They mean if you’re drafting or challenging a statute, you must check for unambiguous language on federal power—otherwise, a court will lean toward protecting state sovereignty and constitutional limits. This prevents accidental overreach into areas like state police powers or First Amendment rights, keeping statutory interpretation grounded in the intended balance between federal and state governments.
Presumption of Constitutionality
The Presumption of Constitutionality directs courts to interpret federal statutes in a manner that avoids constitutional invalidation, assuming Congress acted within its enumerated powers unless a clear constitutional conflict exists. This canon compels a narrow reading of laws that might otherwise encroach on state sovereignty or individual rights, requiring judges to adopt any reasonable construction that upholds the statute’s legality. It operates as a tiebreaker, favoring legislative survival over judicial nullification when ambiguity allows. Effectively, it shifts the burden to the challenger to demonstrate an irreconcilable constitutional defect, reinforcing the judiciary’s deference to the legislature’s constitutional judgment and ensuring statutory preservation under federalism constraints.
Q: How does the Presumption of Constitutionality affect a judge’s approach when a statute’s language is ambiguous?
A: The judge must adopt an interpretation that steers the statute toward constitutional validity, even if a more plausible reading would raise constitutional doubts. This prevents courts from striking down laws unnecessarily, prioritizing legislative intent as constitutionally compatible.
Clear Statement Rule for Preempting State Law
The Clear Statement Rule for Preempting State Law requires Congress to express its intent to override state authority with unmistakable clarity, not mere implication. When interpreting a federal statute, courts apply this canon to protect traditional state police powers. The rule demands that any statute preempting state law contain explicit language or a direct conflict that leaves no room for doubt. To apply it, courts typically follow this sequence:
- Determine if the statute’s text contains an unambiguous statement of preemption.
- If not, examine whether state law creates an actual conflict with federal objectives.
- Resolve ambiguity in favor of preserving state law.
This ensures federalism is not undermined by ambiguous legislative drafting.
Federalism Avoidance and State Sovereignty Concerns
The federalism avoidance canon asks courts to read ambiguous federal laws in a way that doesn’t trample on state sovereignty. When a statute could either preempt state authority or leave it intact, this guideline nudges interpreters to choose the state-friendly option. You avoid assuming Congress intended to disrupt traditional state police powers unless that intent is crystal clear. This keeps the feds from accidentally overstepping into local issues like zoning or family law.
- If a federal law is silent on preemption, it usually leaves states free to enforce their own stricter rules.
- State sovereignty concerns mean agencies must show explicit congressional permission before regulating areas historically left to states.
- Courts often read “savings clauses” as preserving state authority to co-regulate alongside federal schemes.
Presumption Against Congressional Abrogation of Sovereign Immunity
The **Presumption Against Congressional Abrogation of Sovereign Immunity** is a concrete rule in federal statutory interpretation: courts will not read a statute as stripping a state or the federal government of its immunity from private lawsuits unless Congress states that intent in “unmistakably clear” language. For practical application, if you are drafting a claim against a state agency, you must identify a statute that uses explicit terms like “abrogate sovereign immunity” or “consent to suit”—ambiguous phrases like “shall be liable” rarely suffice. This canon forces litigants to scrutinize statutory text before filing, as ambiguous law always falls in favor of the sovereign’s protection.
Q: How does this presumption affect how I read a statute for a lawsuit?
A: It means you cannot rely on general prohibitions or rights-creating language alone. You need a clear, specific waiver of immunity—if you see vague wording, the presumption will defeat your claim before it reaches the merits.
Avoidance of Serious Constitutional Questions
The Avoidance of Serious Constitutional Questions canon directs courts to interpret federal statutes in a manner that sidesteps potential constitutional conflicts, even if an alternative, plausible reading exists. This presumption prioritizes judicial restraint in constitutional adjudication, requiring that a statute be construed to avoid constitutional invalidity unless Congress clearly intended otherwise. Practically, this means a court will not resolve a statutory dispute by declaring a law unconstitutional if it can adopt a narrower construction that avoids the issue entirely. The canon applies only when the constitutional doubt is serious and the alternative interpretation is “fairly possible.” It does not permit courts to distort statutory text or rewrite laws to evade review.
Q: When does the Avoidance of Serious Constitutional Questions canon apply?
A: It applies when a statute is ambiguous and one plausible interpretation would raise a serious constitutional concern; the court must adopt the interpretation that avoids that concern, provided it is not contrary to Congress’s clear intent.
Practical Application Across Agencies and Courts
In practice, federal statutory interpretation guidelines create a unified baseline for agencies and courts, though each applies them with distinct urgency. Agencies rely on these guidelines daily when drafting rules, ensuring their actions survive judicial review under frameworks like *Chevron* or *Skidmore*. Courts, in turn, use the same textualist and purposivist tools to assess whether an agency overstepped its statutory authority. Agencies must document their interpretive reasoning explicitly in administrative records, as courts will scrutinize that logic for consistency with clear statutory language. This cross-institutional dance prevents arbitrary enforcement, demanding that both bodies speak the same interpretive language to maintain lawful governance.
Step Zero: Determining When Chevron Applies
Step Zero: Determining When Chevron Applies is the threshold inquiry that dictates whether an agency’s statutory interpretation receives deference. Practically, you first assess if Congress has directly spoken to the precise question at issue; if the statute is unambiguous, the inquiry ends and Chevron does not apply. If ambiguity exists, verify that the agency’s interpretation was issued through a formal process carrying the force of law, such as notice-and-comment rulemaking or formal adjudication. Merely interpretive rules or policy statements rarely satisfy this precondition, often halting deference before Step One begins. This gatekeeping step forces you to scrutinize both the statutory text’s clarity and the agency action’s procedural pedigree before any deference analysis proceeds.
Major Questions Doctrine and Extraordinary Cases
When applying federal statutory interpretation guidelines, the Major Questions Doctrine and Extraordinary Cases standard demands courts first assess if an agency action has “vast economic and political significance.” Agencies must then demonstrate a clear, specific congressional authorization for such action, as vague or general statutory language will not suffice. An extraordinary case typically addresses a transformative regulatory expansion, such as agency regulation of a major sector of the national economy. This doctrine effectively shifts the interpretive burden, requiring agencies to meet a higher evidentiary threshold before their statutory interpretation is deemed valid.
- Identify if the regulatory action’s scope triggers the “major questions” analysis.
- Congressional intent must be expressly stated, not implied, for extraordinary cases.
- The doctrine applies regardless of the agency’s traditional expertise or procedural steps.
Reconciling Textual Canons with Policy Objectives
Reconciling textual canons with policy objectives requires agencies and courts to treat canons as interpretive starting points, not absolute rules. When a canon like expressio unius est exclusio alterius conflicts with a statute’s stated purpose, practitioners must demonstrate that the canon’s application would undermine the legislative goal. This often involves parsing legislative history to show intent, then arguing that the policy objective should override strict textual inference. The logical test: does the canon produce absurd or unintended consequences? If yes, the objective takes precedence.
Q: How does one prioritize a policy objective over a conflicting textual canon?
A: Show that the canon leads to a result inconsistent with the statute’s plain purpose or recorded intent, using committee reports or enacted findings as direct evidence that Congress expected the policy goal to govern.
Interplay Between Statutory Interpretation and Administrative Procedure Act
The interplay between statutory interpretation and the Administrative Procedure Act dictates how courts review agency rulemaking. When an agency issues a rule, courts first examine whether the statute unambiguously addresses the precise question using traditional interpretive tools like text and structure. If ambiguity exists, the court defers to the agency’s reasonable interpretation under Chevron, but only if the agency followed APA procedural requirements, such as notice-and-comment or reasoned decision-making. This interplay forces agencies to justify interpretive choices within the APA’s framework, ensuring statutory meaning is not determined in isolation.
- Courts apply Chevron only after confirming the APA’s procedural steps were properly completed.
- Statutory ambiguity is assessed using canons of construction before considering agency deference under the APA.
- Agency interpretations that contradict APA procedural mandates (e.g., inadequate reasoning) receive less judicial deference.
Even when a statute is ambiguous, an agency’s interpretive choice must still survive APA arbitrary-and-capricious review.
Judicial Review of Agency Statutory Constructions
In practice, courts apply the familiar Chevron deference framework to evaluate whether an agency’s statutory interpretation is permissible. Under step one, the court independently decides if the statute’s text clearly addresses the precise question; if it does, the agency’s contrary view fails. If Congress’s intent is ambiguous, step two asks whether the agency’s construction is a reasonable one. This two-step analysis forces litigants to frame arguments around statutory clarity first, rather than leading with policy justifications for the agency’s choice. The reviewing court thus exercises a gatekeeping role, allowing agency discretion only when the statute itself leaves interpretive gaps.