Statutory Interpretation: Theories, Tools, and Trends
Released: 2018-04-05T00:00:00

Summary:
In the tripartite structure of the U.S. federal government, it is the job of courts to say what the law is, as Chief Justice John Marshall announced in 1803. When courts render decisions on the meaning of statutes, the prevailing view is that a judge's task is not to make the law, but rather to interpret the law made by Congress. The two main theories of statutory interpretation—purposivism and textualism—disagree about how judges can best adhere to this ideal of legislative supremacy. The problem is especially acute in instances where it is unlikely that Congress anticipated and legislated for the specific circumstances being disputed before the court. While purposivists argue that courts should prioritize interpretations that advance the statute's purpose, textualists maintain that a judge's focus should be confined primarily to the statute's text.
Regardless of their interpretive theory, judges use many of the same tools to gather evidence of statutory meaning. First, judges often begin by looking to the ordinary meaning of the statutory text. Second, courts interpret specific provisions by looking to the broader statutory context. Third, judges may turn to the canons of construction, which are presumptions about how courts ordinarily read statutes. Fourth, courts may look to the legislative history of a provision. Finally, a judge might consider how a statute has been—or will be—implemented. Although both purposivists and textualists may use any of these tools, a judge's theory of statutory interpretation may influence the order in which these tools are applied and how much weight is given to each tool.
This report begins by discussing the general goals of statutory interpretation, reviewing a variety of contemporary as well as historical approaches. The report then briefly describes the two primary theories of interpretation employed today, before examining the main types of tools that courts use to determine statutory meaning. The report concludes by exploring developing issues in statutory interpretation.

subsections: section_title: Introduction
paragraphs: " No vehicles in the park. " 
For decades, lawyers have debated the proper scope of this hypothetical law. The rule at first appears admirably straightforward, but thought experiments applying the law quickly reveal latent complications. Does this law forbid bicycles? Baby strollers? Golf carts? Drones? Does it encompass the service vehicles of the park's caretakers, or an ambulance responding to a parkgoer's injury? Would it prevent the city from bringing in a World War II truck and mounting it on a pedestal as part of a war memorial? While many would read the hypothetical law to prohibit an enthusiastic mother from driving a minivan full of young soccer players into the park, it may not be so simple to justify that seemingly reasonable interperetation. If the soccer mom challenged the decision of a hypothetical Department of Parks and Recreation to prohibit her from entering, how would the Department's lawyers justify this position? Should they refer primarily to the law's text, or to its purpose? What tools should they use to discover the meaning of the text or the lawmaker's purpose? How does their theory of interpretation influence their answers to the harder problems of application?
This deceptively simple hypothetical has endured because it usefully illustrates the challenges of statutory interpretation. Even a statutory provision that at first appears unambiguous can engender significant difficulties when applied in the real world. Supreme Court Justice Felix Frankfurter once aptly described the problem of determining statutory meaning as inherent in "the very nature of words." The meaning of words depends on the context in which they are used and might change over time. Words are "inexact symbols" of meaning, and even in everyday communications, it is difficult to achieve one definite meaning.
These "intrinsic difficulties of language" are heightened in the creation of a statute, which is crafted by a complicated governmental process and will likely be applied to an unforeseeable variety of circumstances. Statutes are usually written in general terms, which may compound the difficulty of applying a provision to specific situations. However, this generality—and the ensuing ambiguity—is often intentional: statutes are frequently drafted to address " categories of conduct." The enacting legislature may have sought to ensure that the statute would be general enough to capture the situations it could not foresee, or may have intended to delegate interpretive authority to the agency responsible for enforcing the statute. Vague or ambiguous language might also be the result of compromise. Or a statute might be silent with respect to a particular application because Congress simply did not anticipate the situation.
When a statute becomes the subject of a dispute in court, judges usually must interpret the law, ambiguous or not. As Chief Justice John Marshall stated in Marbury v. Madison : "It is emphatically the province and duty of the judicial department to say what the law is." Judicial pronouncements about statutes are generally the final word on statutory meaning and will determine how the law is carried out—at least, unless Congress acts to amend the law. In the realm of statutory interpretation, many members of the judiciary view their role in "say[ing] what the law is" as subordinate to Congress's position as the law's drafter. Indeed, the legitimacy of any particular exercise in statutory interpretation is often judged by how well it carries out Congress's will. 
Judges have taken a variety of approaches to resolving the meaning of a statute. The two theories of statutory interpretation that predominate today are purposivism and textualism. Proponents of both theories generally share the goal of adhering to Congress's intended meaning, but disagree about how best to achieve that goal. Judges subscribing to these theories may employ different interpretive tools to discover Congress's meaning, looking to the ordinary meaning of the disputed statutory text, its statutory context, any applicable interpretive canons, the legislative history of the provision, and evidence about how the statute has been or may be implemented. 
Understanding the theories that govern how judges read statutes is essential for Congress to legislate most effectively. As a practical matter, judicial opinions interpreting statutes necessarily shape the way in which those statutes are implemented. If Congress knows how courts ascribe meaning to statutory text, it might be able to eliminate some ambiguity regarding its meaning by drafting according to the predominant legal theories. If Congress follows courts' methodologies for statutory interpretation, it may better communicate its policy choices not only to courts, but also to the general public. Members of the public frequently interpret statutes in the same way as courts, whether because they look to courts as the final arbiters of statutes or because courts often intentionally mimic general understandings of how language is naturally interpreted. Finally, as this report discusses in detail, judges and legal scholars are engaged in an ongoing and evolving debate over the best way to determine the meaning of statutes. For Members of Congress and their staff to participate meaningfully in this discussion, they must be aware of the scope and intricacies of that debate.
To help provide Congress with a general understanding of how courts interpret statutory languge, this report begins by discussing the general goals of statutory interpretation, reviewing a variety of contemporary and historical approaches. The report then describes the two primary theories of interpretation employed today, before examining the main types of tools that courts use to determine statutory meaning. The report concludes by exploring developing issues in statutory interpretation. 
section_title: Goals of Statutory Interpretation: A Historical Overview
paragraphs: Courts "say what the law is" by resolving legal disputes in individual cases. This is true whether a court is interpreting a positive law, such as a statute or regulation, or reasoning from a prior judicial precedent, drawing from a body of law known as the common law. With regard to the common-law tradition of making law through judicial opinions, a court reasons by example, applying general "principles of equity, natural justice, and . . . public policy" to the specific circumstances before the court. Case by case, a common-law court decides more or less anew whether each set of circumstances should follow the rule of a previous decision. But in resolving a statutory dispute, courts generally do not simply determine, based on equity or natural justice, what would have been a reasonable course of action under the circumstances. Instead, the court must "figure out what the statute means" and apply the statutory law to resolve the dispute. 
The predominant view of a judge's proper role in statutory interpretation is one of "legislative supremacy." This theory holds that when a court interprets a federal statute, it seeks "to give effect to the intent of Congress." Under this view, judges attempt to act as "faithful agents" of Congress. They "are not free to simply substitute their policy views for those of the legislature that enacted the statute." This belief is rooted in the constitutional separation of powers: in the realm of legislation, the Constitution gives Congress, not courts, the power to make the law. The judicial power vested in the courts entails only "the power to pronounce the law as Congress has enacted it." Accordingly, courts must remain faithful to what the legislature enacted. 
It was not always the case that judges described their role in statutory interpretation as being so constrained. This section broadly reviews the evolution of statutory interpretation in U.S. courts, noting the various schools of legal thought that predominated at particular periods in the nation's history. However, while these other interpretive theories no longer represent a majority view, all continue to exist in some form today, and critically, they influenced the development of the theories that do dominate modern legal theory. 
subsections: section_title: Early Years: Natural Law and Formalism
paragraphs: Legal thinking in this country's early years was influenced by the idea of natural law, which is the belief that law consists of a set of objectively correct principles derived "from a universalized conception of human nature or divine justice." The goal of judges in a natural law system is to "conform man-made law to those natural law principles." Accordingly, courts looked to "the equity of the statute," seeking to find "the reason or final cause of the law" in order to address "the mischief for which the common law did not provide," but the newly enacted statute did, "and to add life to the cure and remedy, according to the true intent of the makers of the act." 
A distinct, but not mutually exclusive, view of the law that gained popularity in the 19 th century, formalism, posits that "the correct outcome of a case could be deduced" scientifically from fundamental "principles of common law" contained in prior cases. These early formalists believed that they could use established forms of logic, based on these fundamental common-law principles, to determine the meaning of statutory text. 
Both natural law and formalism share the belief that the law provides one right answer to any question and lawmakers can discover that answer. For those who subscribe to these schools of thought, the source of this answer is neither the legislature nor the courts, but the higher principles of law themselves. When natural law and formalism dominated legal thinking, "it did not matter as much whether judges conceived of themselves as faithful agents of Congress or coequal partners in law elaboration." This is because under these theories, both courts and legislators are engaged in the same process of finding the one correct answer. And if courts discover the answer to the legal question presented, proponents of natural law and formalism contend that there is no need to defer to the legislature. Accordingly, under these theories, courts might resort to equity or reason over a strict construction of the language of the statute because this gloss on the legislative text amounts to a "correction" of a defective statute, a correction that would not have been necessary "if the original had been correctly stated." As a result, a prevalent view in the 19 th century was that the judge merely said "what the legislator himself would have said had he been present, and would have put into his law if he had known."
section_title: 20th Century: Rise of Legal Realism
paragraphs: Critically, then, the legitimacy of the theories that primarily governed early American jurisprudence hinged on the belief that a judge could divine the law by focusing on general principles of justice or logic. But as the school of legal realism gained traction in the early 20 th century, legal scholars began to question these assumptions and called for judges to more self-consciously justify the legitimacy of their rulings. The early legal realists sought to discover "how law 'really' operated," applying new insights from the fields of sociology and psychology to judicial decisionmaking. Legal realism led to the widespread recognition that judges sometimes make law, rather than discover it. As a result, judges more readily acknowledged that there were no "pre-established truths of universal and inflexible validity"—or at least, that they could not divine those truths and invariably derive from them the proper conclusion in any given case. For legal realists, there is "no single right and accurate way of reading one case." Accordingly, the need arose for judges to more openly justify the law that they announced in any given case. 
section_title: Modern Jurisprudence: Responding to Legal Realism
paragraphs: In the field of statutory interpretation in particular, legal scholars and judges responded to legal realism in part by distinguishing the law-making role of the legislature from the law-interpreting role of the court. In this realm especially, "law" was not some platonic ideal, but instead was the statute that Congress had passed. Justice Oliver Wendell Holmes famously expressed this shift in prevailing legal theory when he stated, "[t]he common law is not a brooding omnipresence in the sky but the articulate voice of some sovereign or quasi sovereign that can be identified . . . ." 
Judges noted that the Constitution itself restrained judicial discretion by designating Congress, not the courts, as the lawmaking branch. And because Congress made the law, judges argued that they should restrain themselves to act "as merely the translator of another's command." As Justice Frankfurter asserted: "In a democracy the legislative impulse and its expression should come from those popularly chosen to legislate, and equipped to devise policy, as courts are not." Rather than seeking to discover foundational principles of the law, as determined by judges, many legal theorists argued that courts should instead attempt "to discover the rule which the law-maker intended to establish; to discover the intention with which the law-maker made the rule, or the sense which he attached to the words wherein the rule is expressed." To do otherwise was to risk attempting to make policy, usurping the legislative function. Today it is widely accepted that it is inappropriate for judges to prioritize their own policy views over the policy actually codified by the legislature. This general view undergirds both modern purposivism and modern textualism. 
Not all legal scholars and judges, however, reacted to legal realism by adopting a view of legislative supremacy in statutory interpretation. A smaller but influential number argued instead that if judges make law, they should openly embrace this role and seek to make good law. This school of thought, which continues today, points out that the Constitution has granted to judges the power of interpretation and argues that the constitutional duty of interpretation entails a meaningful duty to shape the law. For example, legal scholar William Eskridge has claimed that the Constitution purposefully "divorces statutory interpretation (given to the executive and the courts in articles II and III) from statutory enactment (by Congress under article I)," in order to ensure "that statutes will evolve because the perspective of the interpreter will be different from that of the legislator." 
At least one commentator has characterized Eskridge's theory of "pragmatic dynamism" as a revival of the natural law tradition of equitable interpretation. Judge Guido Calabresi, while a professor at Yale Law School, argued that judges should take an active role in determining whether statutes are "out of phase with the whole legal framework," and should have "the authority to treat statutes as if they were no more and no less than part of the common law." Former federal judge Richard Posner, another pragmatist, has similarly argued that judges should take into account their "intuitions" or "preconceptions," and look to the practical consequences of their decisions in determining how to read a statute.
section_title: Major Theories of Statutory Interpretation
paragraphs: The two predominant theories of statutory interpretation today are purposivism and textualism. As discussed, both theories share the same general goal of faithfully interpreting statutes enacted by Congress. This goal is grounded in the belief that the Constitution makes the legislature the supreme lawmaker and that statutory interpretation should respect this legislative supremacy. Interpretive problems arise, however, when courts attempt to determine how Congress meant to resolve the particular situation before the court. The actual intent of the legislature that passed a given statute is usually unknowable with respect to the precise situation presented to the court. Accordingly, purposivists and textualists instead seek to construct an objective intent.
Purposivists and textualists, however, disagree about the best way to determine this objective intent. This disagreement is based in large part on distinct views of the institutional competence of the courts. The concept of "institutional competence" assumes that each branch of government "has a special competence or expertise, and the key to good government is not just figuring out what is the best policy, but figuring out which institutions should be making which decisions and how all the institutions should interrelate." "[T]he rules of [statutory] interpretation allocate lawmaking power among the branches of government, and those rules should reflect and respect what, if anything, the Constitution has to say about that allocation." Consequently, because purposivists and textualists have different views of how judges can best act to advance the will of the legislature, they advocate different modes of interpretation and turn to different tools for evidence of Congress's objective intent. 
subsections: section_title: Purposivism
paragraphs: Purposivists argue "that legislation is a purposive act, and judges should construe statutes to execute that legislative purpose." Purposivists often focus on the legislative process, taking into account the problem that Congress was trying to solve by enacting the disputed law and asking how the statute accomplished that goal. They argue that courts should interpret ambiguous text "in a way that is faithful to Congress's purposes." Two preeminent purposivists from the mid-20 th century, Henry Hart and Albert Sacks, advocated the "benevolent presumption . . . that the legislature is made up of reasonable men pursuing reasonable purposes reasonably." But there was a caveat to this presumption: it should not hold if "the contrary is made unmistakably to appear" in the text of the statute.
Purposivists believe that judges can best observe legislative supremacy by paying attention to the legislative process. The Constitution "charges Congress, the people's branch of representatives, with enacting laws," and accordingly, purposivists contend that courts should look to "how Congress actually works." As such, they argue that to preserve the "integrity of legislation," judges should pay attention to "how Congress makes its purposes known, through text and reliable accompanying materials constituting legislative history." Courts should take into consideration any "institutional device that facilitates compromise and helps develop the consensus needed to pass important legislation." As one purposivist judge has said, "[w]hen courts construe statutes in ways that respect what legislators consider their work product, the judiciary not only is more likely to reach the correct result, but also promotes comity with the first branch of government."
To discover what a reasonable legislator was trying to achieve, purposivists rely on the statute's "policy context," looking for "evidence that goes to the way a reasonable person conversant with the circumstances underlying enactment would suppress the mischief and advance the remedy." Purposivists are more willing than textualists to consider legislative history. But arguably, the core of purposivism is "reasoning by example" and asking whether various specific applications of the statute further its general purpose. As a result, purposivists maintain that courts should first ask what problem Congress was trying to solve, and then ask whether the suggested interpretation fits into that purpose. Hart and Sacks suggested that judges should seek "to achieve consistency of solution . . . to make the results in the particular cases respond to . . . some general objective or purpose to be attributed to the statute." Judges should look for interpretations that promote "coherence and workability."
Detractors argue that it is likely impossible to find one shared intention behind any given piece of legislation, and that it is inappropriate for judges to endeavor to find legislative purpose. Such critics claim that judges are not well-equipped to understand how complex congressional processes bear on the law finally enacted by Congress—not least because the records of that process, in the form of legislative history, are often internally contradictory and otherwise unreliable. Opponents of purposivism also sometimes argue that the theory is too easily manipulable, allowing the purposivist to ignore the text and "achieve what he believes to be the provision's purpose."
section_title: Textualism
paragraphs: In contrast to purposivists, textualists focus on the words of a statute, emphasizing text over any unstated purpose. Textualists argue courts should "read the words of that [statutory] text as any ordinary Member of Congress would have read them." They look for the meaning "that a reasonable person would gather from the text of the law, placed alongside the remainder of the corpus juris [the body of law]." Textualists care about statutory purpose to the extent that it is evident from the text. Accordingly, textualists "look at the statutory structure and hear the words as they would sound in the mind of a skilled, objectively reasonable user of words."
Textualists believe that "judges best respect[] legislative supremacy" when they follow rules that prioritize the statutory text. For textualists, focusing on the text alone and adopting the "presumption that Congress 'means . . . what it says' enables Congress to draw its lines reliably—without risking that a court will treat an awkward, strange, behind-the-scenes compromise as a legislative error or oversight." As Judge Frank Easterbrook stated, "[s]tatutes are not exercises in private language," but are "public documents, negotiated and approved by many parties." Textualism focuses on the words of a statute because it is that text that survived these political processes and was duly enacted by Congress, exercising its constitutional power to legislate. Textualists have argued that focusing on "genuine but unexpressed legislative intent" invites the danger that judges "will in fact pursue their own objectives and desires" and, accordingly, encroach into the legislative function by making, rather than interpreting, statutory law.
To discover what a reasonable English-speaker would think a statute's text means, textualists look for evidence of the statute's "semantic context," seeking "evidence about the way a reasonable person conversant with relevant social and linguistic practices would have used the words." Many textualists decline to use legislative history under most circumstances. Instead, textualist judges generally seek to discover "the shared conventions" that are inherent in the statutory language, asking what "assumptions [were] shared by the speakers and the intended audience." As evidence of these shared assumptions, textualists might turn to rules of grammar, or to the so-called "canons of construction" that "reflect broader conventions of language use, common in society at large at the time the statute was enacted."
Critics of textualism argue that the theory is an overly formalistic approach to determining the meaning of statutory text that ignores the fact that courts have been delegated interpretive authority under the Constitution. Opponents of textualism sometimes claim that Congress legislates with this background understanding, expecting courts to pay attention to legislative processes and the law's purpose when applying it to specific circumstances. As a result, textualism's detractors argue that considering evidence of a statute's purpose can be more constraining on a judge than merely considering the text, divorced from evidence of legislative intent.
section_title: Purposivism vs. Textualism In Practice
subsections: section_title: A Clear Distinction
paragraphs: The distinctions between these two theories were illustrated in the Supreme Court case of Arlington Central School District Board of Education v. Murphy . The case arose out of a suit in which a student's parents had successfully sued a school district under the Individuals with Disabilities Education Act. As relevant to the case, that Act provided that "a court 'may award reasonable attorneys' fees as part of the costs' to parents who prevail in an action brought under the Act." The parents sought to recover fees paid to an expert in education who had provided assistance throughout the proceedings. The issue before the Court was whether the Act "authorized the compensation of expert fees."
In a textualist opinion written by Justice Alito, the majority of the Court concluded that the Act did not authorize the compensation of expert fees. Emphasizing that courts must "begin with the text" and "enforce [that text] according to its terms," the Court stated that the provision "provides for an award of 'reasonable attorneys' fees,'" without "even hint[ing]" that the award should also include expert fees. The majority opinion rejected the parents' arguments that awarding expert fees would be consistent with the statute's goals and its legislative history, "in the face of the [Act's] unambiguous text."
By contrast, Justice Breyer's dissenting opinion embodied a purposivist approach to interpreting the statute. He concluded that the disputed term "costs" should be interpreted "to include the award of expert fees" for two reasons: "First, that is what Congress said it intended by the phrase. Second, that interpretation furthers the [Act's] statutorily defined purposes." Justice Breyer relied on the bill's legislative history and the Act's "basic purpose"—to guarantee that children with disabilities receive quality public education—as primary evidence of the statute's meaning. He did not agree that the statute's text was unambiguous. Although he noted that a literal reading of the provision would not authorize the costs sought by the parents, he concluded that this reading was "not inevitable." Instead, he concluded that his reading, "while linguistically the less natural, is legislatively the more likely."
section_title: A Convergence of Theories?
paragraphs: Many judges, however, do not necessarily identify as pure purposivists or textualists; or even if they do, in practice, they will often employ some elements from each theory. Some scholars have argued that even the theoretical gap between these two theories is narrowing. Most modern purposivists consider the statutory text to be both a starting point and an ultimate constraint. And most textualists will look past the plain text, standing alone, to discover the relevant context and determine what problem Congress was trying to address. 
One Supreme Court case issued in 2017 demonstrates the increasing similarities between the two factions, as well as the remaining distinctions. In NLRB v. SW General, Inc. , the Supreme Court considered whether the service of the Acting General Counsel of the National Labor Relations Board violated a statute that limits the ability of federal employees to serve as "acting officers." The case presented a question of statutory interpretation, and the majority and dissenting opinions both began their analysis with the statutory text before proceeding to consider many of the same sources to determine the meaning of the disputed statute. 
The majority opinion in SW General , authored by Chief Justice John Roberts, principally represents a textualist point of view, although it also includes some elements of purposivism. In describing the facts of the case, the Chief Justice began with an explanation of the problem that Congress faced when it first enacted the disputed statute, and, in so doing, considered the original version of that statute and subsequent amendments intended to address continuing disputes over the ability of federal employees to serve as acting officers. The Court began its analysis with the statutory text, considering its meaning by looking to the ordinary meaning of the words, rules of grammar, and statutory context. The Court emphasized two "key words" in the disputed provision. The majority then noted that it did not need to consider the "extra-textual evidence" of "legislative history, purpose, and post-enactment practice" because the text was clear. Nonetheless, the Court went on to evaluate and reject this evidence as "not compelling." Ultimately, the majority held that the acting officer's service violated the relevant statute. 
In dissent in SW General, Justice Sonia Sotomayor concluded that the "text, purpose, and history" of the statute suggested the opposite conclusion. Like the majority opinion, the dissent began by considering the meaning of the text, and acknowledged that "taken in isolation," certain words could support the majority's reading. However, Justice Sotomayor concluded that two textual canons of construction implied that the statute should be read differently in light of the full statutory context. Additionally, while the dissenting opinion similarly considered "the events leading up to" the enactment of the relevant statute, Justice Sotomayor also placed some weight on the historical practice of the executive department after the passage of the statute. The dissent used the provision's legislative history to inform its understanding of the historical practice under the statute, in its earlier and current forms, and reached a different conclusion from the majority opinion. As a result, the dissent represents a more purposivist view of the case, but one that still concentrated on the statutory text.
As SW General illustrates, the particular tools a judge uses to discover evidence about the meaning of the statute, and the weight that the judge gives to that evidence, can influence the outcome of a case. In contrast to the opinions of Justices Alito and Breyer in Arlington Central School District , the two opinions in SW General considered many of the same interpretive tools, and the text of the statute was central to both opinions. However, like the textualist majority opinion in Arlington Central School District , the textualist majority opinion in SW General noted that legislative history is disfavored where the text is clear, giving less weight to this tool than the dissenting opinion. These cases demonstrate that if a judge's theory of statutory interpretation counsels that some tools should be preferred over others, that theory can change the way the judge resolves a particular dispute.
section_title: Tools of Statutory Interpretation
paragraphs: Judges use a variety of tools to help them interpret statutes, most frequently relying on five types of interpretive tools: ordinary meaning, statutory context, canons of construction, legislative history, and evidence of the way a statute is implemented. 
These tools often overlap. For example, a judge might use evidence of an agency's implementation of a statute to support her own understanding of a word's ordinary meaning. And basic principles about understanding statutory context are sometimes described as canons of construction.
Some theories of statutory interpretation counsel that certain tools are generally disfavored; for example, textualism teaches that judges should only rarely look to legislative history. Consequently, a judge's interpretive theory might influence which tools she uses. Different judges, then, might unearth different evidence about the meaning of a particular statute, and even if they find the same evidence, they might consider it in different ways. However, in practice, judges will often draw on whatever tools provide useful evidence of the meaning of the statute before them. 
subsections: section_title: Ordinary Meaning
paragraphs: Courts often begin by looking for the "ordinary" or "plain" meaning of the statutory text. Where a term is not expressly defined in the statute, courts generally assume "that Congress uses common words in their popular meaning, as used in the common speech of men." Thus, for example, in the context of a case that raised the question of what it meant to "use" a gun, Justice Scalia stated the following in a dissenting opinion: 
To use an instrumentality ordinarily means to use it for its intended purpose. When someone asks, "Do you use a cane?," he is not inquiring whether you have your grandfather's silver-handled walking stick on display in the hall; he wants to know whether you  walk  with a cane. Similarly, to speak of "using a firearm" is to speak of using it for its distinctive purpose,  i.e. , as a weapon.
The Supreme Court has also referred to this exercise as seeking a word's "natural meaning," or its "normal and customary meaning." However, this "ordinary meaning" presumption can be overcome if there is evidence that the statutory term has a specialized meaning in law or in another relevant field. 
Judges may use a wide variety of materials to gather evidence of a text's ordinary meaning. In many cases, "simple introspection" suffices, as judges are English speakers who presumably engage in everyday conversation like the rest of the general public. Judges also turn to dictionaries to help inform their understanding of a word's normal usage. Judges may then have to choose between multiple definitions provided by the same dictionary or by different dictionaries. Courts have also turned to books to discover a word's ordinary meaning, drawing from works such as Moby Dick or the Bible as well as Aesop ' s F ables and the work of Dr. Seuss. Finally, judges may look for evidence of normal usage elsewhere in the law, such as in judicial decisions or in other governmental materials. 
The idea that courts should generally give the words of a statute their "usual" meaning is an old one. This principle straddles judicial philosophies: for example, all current members of the Supreme Court have regularly invoked this rule of ordinary meaning. If Congress does in fact generally use words as they would be normally understood, this interpretive tool helps judges act as faithful agents of Congress by ensuring that judges and Congress—along with the ordinary people governed by statutes—are looking to the same interpretive context: "normal conversation."
Although there is wide judicial consensus on the general validity of this rule, disputes arise in its application. To say that a statutory word should be given the same meaning that it would have in "everyday language" serves only as a starting point for debate in many cases. The ordinary meaning of a term may often be "clear," or uncontroversial in its application to some core set of circumstances. Some have argued that invoking a word's plain meaning in these cases is tautological, equivalent to saying that "[w]ords should be read as saying what they say." Moreover, at the margins, when a court is no longer considering a prototypical example of the disputed statutory term, the judge is called upon to explain how the statute applies to the facts before the court. Therefore, in some cases, merely adverting to the ordinary meaning tool may not help illuminate a statutory term.
There are also a number of theoretical criticisms of the "ordinary meaning" standard. Some have argued that judges might invoke "ordinary meaning" merely to mask their own policy preferences. As Judge Easterbrook has claimed, frequently, "[t]he invocation of 'plain meaning' just sweeps under the rug the process by which meaning is divined." Because "ordinary meaning" invites judges to refer to their own experiences as English speakers, it is arguably susceptible to the importation of personal policy preferences. As a result, if a judge fails to justify an assertion about the ordinary meaning of a term, the underlying opinion could be vulnerable to attack on that basis.
section_title: Statutory Context
paragraphs: Often, a statutory dispute will turn on the meaning of only a few words. Courts will interpret those words, though, in light of the full statutory context. To gather evidence of statutory meaning, a judge may turn to the rest of the provision, to the act as a whole, or to similar provisions elsewhere in the law. As the Supreme Court said in one opinion, "Statutory construction . . . is a holistic endeavor. A provision that may seem ambiguous in isolation is often clarified by the remainder of the statutory scheme. . . ."
For instance, a court might look to see whether the disputed language is used in another statutory provision. Courts will generally try to give identical terms the same meaning throughout a statute, and another provision may offer context that illuminates the meaning of the relevant term. However, this rule calling for words to be defined consistently is defeasible, again depending on the context: "A given term in the same statute may take on distinct characters from association with distinct statutory objects calling for different implementation strategies." A judge might also look to the rest of the statute to find whether Congress used different language in other provisions. If Congress elsewhere used language that more clearly captured an interpretation urged by one of the parties, it might suggest that the disputed term should not be given that construction. Courts will generally read as meaningful "the exclusion of language from one statutory provision that is included in other provisions of the same statute."
Thus, statutory context can supply evidence of semantic, or text-focused, context. In Smith v. United States , for example, a defendant challenged his sentence following conviction for a drug trafficking offense during which he offered to trade a gun for cocaine. The Supreme Court had to decide whether the defendant should be subject to a sentence enhancement that applied to any "'use' of a firearm 'during and in relation to . . . [a] drug trafficking crime.'" The defendant argued that this enhancement should apply only when a firearm was "used as a weapon," not when it was used to barter for drugs. The Supreme Court disagreed.
During the course of its analysis, the Court investigated how Congress had employed the term "use" in other provisions of the statute. The Court found it compelling that a different subsection of the statute called for forfeiture of a firearm that was "used" in an interstate transfer of a firearm or in a federal offense involving the exportation of a firearm. In the eyes of the Court, this other provision clearly contemplated that firearms could be "used" "as items of commerce rather than as weapons," suggesting the same interpretation of "used" should apply to the disputed sentence enhancement. The Court also noted that Congress had used the phrase "involved in" instead of the word "use" elsewhere in the statute. Specifically, a different provision allowed the seizure of a firearm that was "'involved in' . . . the making of a false statement material to the lawfulness of a gun's transfer." The Court reasoned that this distinction demonstrated that Congress found it was necessary in the other provision to use more expansive language because "making a material misstatement in order to acquire or sell a gun is not 'use' of the gun." By contrast, Congress "did not so expand the language for offenses in which firearms were 'intended to be used ,' even though the firearms in many of those offenses function as items of commerce rather than as weapons." Therefore, according to the majority opinion, "Congress apparently was of the view that one could use a gun by trading it."
Statutory context can also help a court determine how the disputed terms fit into the rest of the law, illuminating the purpose of a provision. Courts may consider statutory declarations of purpose as well as the broad functioning of the statutory scheme. Judges sometimes weigh the practical consequences of the various proposed interpretations. It could be that "only one of the permissible meanings produces a substantive effect that is compatible with the rest of the law." This use of statutory context often implicates the broader debate between purposivism and textualism, as well as arguments over when judges should use practical consequences to determine statutory meaning. 
section_title: Canons of Construction
paragraphs: Over time, courts have created the "canons of construction" to serve as guiding principles for interpreting statutes. The canons supply default assumptions about the way Congress generally expresses meaning, but are not "rules" in the sense that they must invariably be applied. A judge may decline to interpret a statute in accordance with any given canon if the canon's application is not justified in that case. Some judges, especially purposivists and some pragmatists, may even doubt the general validity of the canons as interpretive rules. However, the canons are widely used and defended.
Just as the justifications for using the canons of construction vary, so may judges disagree on what qualifies as a valid canon, either as a matter of theory or historical fact. These disagreements will sometimes stem from a judge's individual theory of statutory interpretation. This report's Appendix combines two preeminent anthologies of the canons of construction, providing a list of the widely accepted canons of construction. However, even the authors of these prominent lists disagree about whether certain canons are valid. This report does not attempt to set out a definitive compilation of the canons of construction, but merely describes the canons generally, giving examples where appropriate. 
Generally, legal scholars and judges divide the canons into two groups: semantic and substantive canons.
subsections: section_title: Semantic Canons
paragraphs: The semantic, or textual, canons represent "rules of thumb for decoding legal language." Because these canons focus on statutory text, they are often favored by textualists. The semantic canons frequently reflect the rules of grammar that govern ordinary language usage. Consequently, these rules may overlap with indicators of a provision's ordinary meaning —and indeed, some authors label the principle that words should be given their ordinary meaning as a semantic canon. But there are a greater number of semantic canons beyond the ordinary meaning rule, several of which are discussed below.
For example, the "grammatical 'rule of the last antecedent'" states that "a limiting clause or phrase . . . should ordinarily be read as modifying only the noun or phrase that it immediately follows." In Barnhart v. Thomas , the Supreme Court illustrated this canon with the following hypothetical: 
Consider, for example, the case of parents who, before leaving their teenage son alone in the house for the weekend, warn him, "You will be punished if you throw a party or engage in any other activity that damages the house." If the son nevertheless throws a party and is caught, he should hardly be able to avoid punishment by arguing that the house was not damaged. The parents proscribed (1) a party, and (2) any other activity that damages the house. 
The last-antecedent canon tells the reader of the parents' edict that the descriptive clause "that damages the house" refers to the "nearest reasonable antecedent": here, "any other activity." Accordingly, that clause modifies only the phrase "any other activity," and not "party," a more remote antecedent.
In a more recent case, Lockhart v. United States , the Supreme Court applied the last-antecedent canon to interpret a federal criminal statute that imposed a 10-year mandatory minimum sentence on any person convicted of violating a statute prohibiting the possession of child pornography, if that person had "a prior conviction . . . under the laws of any State relating to aggravated sexual abuse, sexual abuse, or abusive sexual conduct involving a minor or ward." The question before the Court was "whether the limiting phrase that appears at the end of that list—"involving a minor or ward"—applies to all three predicate crimes preceding it in the list or only the final predicate crime." Invoking the rule of the last antecedent, the Court concluded that the limiting phrase "modifies only the phrase that it immediately follows: 'abusive sexual conduct.'" 
The dissenting opinion in Lockhart argued that a different semantic canon, the "series-qualifier canon," applied instead of the last-antecedent canon. The "series-qualifier" canon provides that under certain circumstances, a modifier should be applied to all terms in a list. Because the modifying clause "involving a minor or ward" followed "a list of multiple, parallel terms," the dissent claimed that it should apply to the entire series. In the dissenters' view, "the reference to a minor or ward applies as well to sexual abuse and aggravated sexual abuse as to abusive sexual conduct." By contrast, the majority of the Court believed the series-qualifier canon was inapplicable, concluding that the disputed provision "does not contain items that readers are used to seeing listed together or a concluding modifier that readers are accustomed to applying to each of them." Further, the majority argued, "the varied syntax of each item in the list makes it hard for the reader to carry the final modifying clause across all three."
Another semantic canon, the rule against surplusage, relies less on the niceties of grammar and more on the general principles underlying how courts assume Congress conveys meaning. The surplusage canon requires courts to give each word and clause of a statute operative effect, if possible. Stated another way, courts should not interpret any statutory provision in a way that would render it or another part of the statute inoperative or redundant. Accordingly, for example, when a court is faced with a statutory list of terms, it generally will read each term to convey some distinct meaning. In Bailey v. United States , the Supreme Court considered a statute that imposed a five-year mandatory minimum sentence on a person who "uses or carries a firearm" during a crime of violence or drug trafficking crime. The Court refused to give the term "use" such a broad reading that "no role remains for 'carry.'" Instead, the Court assumed "that Congress used two terms because it intended each term to have a particular, nonsuperfluous meaning," and gave "use" a more limited connotation that "preserve[d] a meaningful role for 'carries' as an alternative basis for a charge." But elsewhere, judges have questioned whether the assumption underlying the surplusage canon is true or whether instead it is more likely that Congress sometimes does use redundant language, possibly to make doubly sure that a statute covers certain circumstances.
section_title: Substantive Canons
paragraphs: In contrast to the semantic canons, the substantive canons express "judicial presumption[s] . . . in favor of or against a particular substantive outcome." Some of these canons, primarily those that protect constitutional values, are frequently described as "clear statement rules" because courts will favor certain outcomes unless the statute makes a "clear statement" that unambiguously dislodges the presumption. The substantive canons "look to the legal consequences of interpretation rather than to linguistic issues alone." If a statute is susceptible to more than one meaning, they may tip the scale toward a particular result.
Accordingly, invocation of the substantive canons frequently invites judicial disagreement. The canon of constitutional avoidance provides a good example of how even a well-established substantive canon can provoke debate. The canon of constitutional avoidance provides that if one plausible reading of a statute would raise "serious doubt" about the statute's constitutionality, a court should look for another, "fairly possible" reading that would avoid the constitutional issue. Thus, for instance, the constitutional-avoidance canon might lead a court to adopt a limiting construction of a statutory provision, if a broader interpretation would allow the government to exercise a constitutionally problematic amount of power. 
The constitutional-avoidance canon may allow a court to adopt a "reasonable alternative interpretation" even if it is not otherwise "the most natural interpretation" of the disputed statute. For example, in Bond v. United States , the Supreme Court interpreted a statute making it a crime for a person to use "any chemical weapon." The Court noted that the "expansive language" of the statute could be read to encompass the conduct of the defendant, who had placed toxic chemicals on the car door, mailbox, and door knob of a friend after discovering that the friend had become pregnant by the defendant's husband. However, the Court decided that it would not interpret the statute "to reach purely local crimes" because such an interpretation would intrude on powers traditionally reserved for the states, implicating constitutional concerns about the balance of power between the federal government and the states. Instead, the Court read the statute more narrowly, to exclude the defendant's conduct. 
Of course, judges may disagree on whether an alternative reading that avoids a constitutional problem is "fairly possible." As the Supreme Court recently emphasized, the constitutional-avoidance canon "does not give a court the authority to rewrite a statute as it pleases."
Many of the substantive canons entail difficult judgments in determining whether triggering threshold conditions have been met. In the case of the canon of constitutional avoidance, a court need not conclude that a suggested reading of the statute in fact would render the statute unconstitutional; the canon requires only that there is a "serious doubt" about the constitutionality of the proferred interpretation. Judges disagree, however, on how much constitutional "doubt" must be present before a court may use the constitutional-avoidance canon to support a certain interpretation of a statute. As one treatise puts it: "How doubtful is doubtful?"
More generally, judges frequently disagree about whether substantive canons are appropriately used to interpret statutes, both in theory and in practical application. This disagreement sometimes stems from different beliefs about the general justifications for using the canons. To the extent that the substantive canons suggest that a judge should read a statute in a way that is not immediately evident from the statute's text or purpose, both textualists and purposivists may be wary of employing these canons. Consequently, most courts will not apply the substantive canons unless they conclude that after consulting other interpretive tools, the statute remains ambiguous. Again, however, such a conclusion often presents a debatable question about whether a statute is sufficiently ambiguous to call for the application of a substantive canon.
section_title: Justifications: Disrepute and Rehabilitation
paragraphs: Judges may choose not to apply a canon to resolve a statutory ambiguity if they disagree with the justifications generally proffered to justify that canon, or if they simply believe that those general justifications do not warrant its extension to the case before them. The canons of construction were a disfavored tool of statutory interpretation for a significant portion of the 20 th century. This view was reflected in an influential article written by legal scholar Karl Llewellyn in 1950, in which he argued that the canons were not useful interpretive tools because of their indeterminacy. He compiled a table of "thrusts" and "parries" that purported to demonstrate that for every canon, there was an opposing canon on the same point. For example, one thrust declares that "[w]ords and phrases which have received judicial construction before enactment are to be understood according to that construction," while the parry counters, "[n]ot if the statute clearly requires them to have a different meaning." Some modern judges have agreed with this criticism, arguing that judges effectively "need a canon for choosing between competing canons." 
Others, however, have challenged Llewellyn's list, questioning the validity of the rules that he claimed were canons. Scholars and judges have also cast doubt on whether his thrusts and parries are truly contradictory, arguing that many of his pairs instead represent two halves of one rule, the thrust giving the general rule, and the parry, the exception or condition. By and large, the canons of construction have been rehabilitated among jurists and legal scholars, primarily by textualists, who have argued on a number of bases that the canons represent "sound interpretive conventions." 
The foregoing criticisms, however, have forced many judges to more diligently justify their use of the canons. One scholar, Caleb Nelson, has placed the canons into two categories based on the justifications given for their canonization. For Nelson, the first group of canons is descriptive; such canons "simply reflect broader conventions of language use, common in society at large at the time the statute was enacted." Judges invoke these canons because, according to this scholar, they are so often accurate descriptions of the way that all people use words. As a result, courts expect that these principles will also apply to legislative drafting. Nelson describes the second group of canons as normative. These normative canons are "used primarily by lawyers" rather than society at large and "relate specifically to the interpretation of statutes." Courts may think that these canons, as well, accurately capture insights about congressional behavior. But judges might also apply these canons as a matter of historical practice, or because they believe the canons reflect good policy, or because they believe the canons provide principles that limit judicial deference and promote predictability in judicial decisionmaking. 
Defenders of the canons have argued that they help judges act as faithful agents of the legislature, either because they reflect legislative drafting practices or because they provide coordinating background rules that can guide Congress when drafting legislation. For example, the constitutional-avoidance canon is frequently said to respect legislative supremacy —although judges do not always agree on the reasons why. The Court has, at times, said that the constitutional-avoidance canon reflects what Congress meant because Congress would not have wanted to enact an unconstitutional statute. Choosing a reasonable alternative interpretation "recognizes that Congress, like [the courts], is bound by and swears an oath to uphold the Constitution." Others have argued that even if the canon does not reflect actual congressional practice, it properly represents a judicial policy judgment "that courts should minimize the occasions on which they confront and perhaps contradict the legislative branch." Some judges, however—primarily purposivists—have argued for greater caution in deploying the canons of construction, warning that insofar as they do not reflect the reality of legislative drafting, they may not respect legislative supremacy. 
Even if a judge agrees that a particular canon is generally valid, the court may still doubt that it should control the interpretation of a particular statute. Modern theory acknowledges that the application of a particular canon in any case is highly context-dependent. The canons merely supply "one indication" of meaning, suggesting only that "a particular meaning is linguistically permissible, if the context warrants it." Judges sometimes describe the canons as akin to rebuttable presumptions. Judges will weigh application of the canon against the evidence of statutory meaning discovered through other interpretive tools and may disagree about whether a canon is so contrary to other indicators of meaning that it should not be applied. The use of the canons "rest[s] on reasoning," and their application should be justified in any given case. 
A judge's willingness to deploy a particular canon, generally or in a specific case, may also depend on that judge's particular theory of interpretation. Many judges will turn to the canons only if their most favored tools fail to resolve any ambiguity. For example, Justice Clarence Thomas, who is generally described as a textualist, has stated the following: 
[C]anons of construction are no more than rules of thumb that help courts determine the meaning of legislation, and in interpreting a statute a court should always turn first to one, cardinal canon before all others. We have stated time and again that courts must presume that a legislature says in a statute what it means and means in a statute what it says there. 
Acccordingly, in a decidedly textualist opinion for the Court in Connecticut Nat iona l Bank v. Germain , Justice Thomas concluded that because the statutory text was clear, the canon against surplusage was inapplicable. 
In a similar vein, Justice William Brennan argued that it was unnecessary to invoke the canon of constitutional avoidance in his dissenting opinion in NLRB v. Catholic Bishop of Chicago . In particular, he contended that the alternative reading adopted by the majority was not a "fairly possible" interpretation of the statute, relying heavily on the statute's legislative history to demonstrate that Congress intended to foreclose the majority opinion's construction. Thus, although a particular canon might facially operate to resolve a particular statutory ambiguity, judges may disagree about whether a canon's application is appropriate, if another interpretive tool suggests the statute should bear another meaning and if a particular jurisprudential methodology counsels for reliance on that particular tool. 
section_title: Legislative History
paragraphs: Where the text of the statute alone does not answer the relevant question, judges have at times turned to a statute's legislative history, defined as the record of Congress's deliberations when enacting a law. One of the Supreme Court's most famous—and perhaps infamous —invocations of legislative history came in United Steelworkers v. Weber . In that case, the Court considered whether Title VII of the Civil Rights Act of 1964, which "make[s] it unlawful to 'discriminate . . . because of . . . race' in hiring" and training employees, prohibited a private employer from adopting an affirmative action plan intended to increase the number of black employees in one of its training programs. The Court noted that "a literal interpretation" of the relevant statutory provisions arguably would forbid such plans, since they "discriminate[d] against white employees solely because they [were] white." Nonetheless, the Court concluded that in this case, such a "literal construction" was "misplaced." Instead, writing for the majority, Justice Brennan used the legislative history of Title VII to uncover evidence of the statute's purpose, examining a number of statements from individual Senators as well as the committee report. He concluded that the law sought to "address centuries of racial injustice," and Congress could not have "intended to prohibit the private sector from taking effective steps to accomplish the goal that Congress designed Title VII to achieve." In Justice Brennan's view, the private employer's plan mirrored the purposes of the statute by seeking "to abolish traditional patterns of racial segregation and hierarchy," and the legislative history demonstrated that Congress intended to leave an "area of discretion" for just such a plan.
subsections: section_title: Purposes for Using Legislative History
paragraphs: The use of legislative history has generated significant debate over the past century. In its most controversial applications, legislative history has been deployed in opinions that cite a statute's purpose to override arguably clear text, as demonstrated by Weber . Most frequently, however, when judges use legislative history, it is not necessarily to contradict a clear text, but to discover evidence of an ambiguous statute's underlying purpose. As with the substantive canons, courts have suggested that legislative history should not be examined unless the statutory text is ambiguous. Of course, judges may disagree whether the text is sufficiently ambiguous to warrant recourse to a statute's legislative history. Judges have also used legislative history to support a textual interpretation. 
Judges do not always use legislative history to determine a statute's purpose . Even textualist judges may use legislative history to determine whether a statutory term has a specialized meaning or to determine whether a seemingly incongruous result nonetheless aligns with congressional intent. Some judges may also use legislative history to determine the scope of a statute and ascertain whether Congress sought to address the particular problem before the court at all. Thus, for example, in FDA v. Brown & Williamson Tobacco Corp . , the Court reviewed the history of various "tobacco-specific legislation that Congress ha[d] enacted over the past 35 years," along with the history of the disputed provision located in the agency's organic statute, the Federal Food, Drug, and Cosmetic Act (FDC&A). In the Court's view, the fact that the other legislative acts specifically concerned the issue of tobacco bore directly on the meaning of the FDC&A, which did not expressly address tobacco. The Court concluded that Congress did not intend to give the FDA jurisdiction to broadly regulate tobacco products in the FDC&A.
section_title: The Debate over Using Legislative History
paragraphs: To the extent that legislative history is used to determine statutory purpose, purposivists and textualists may disagree about whether legislative history is a permissible tool of statutory interpretation. Many purposivists defend the use of legislative history on the grounds that these deliberative materials can illuminate the context and purpose of a statutory provision. Purposivists emphasize legislative process, and legislative history provides a record of that process. Defenders of legislative history generally argue that in statutory interpretation, judges should respect the processes Congress has established and should pay attention to those materials that Congress itself has used to memorialize the lawmaking process. Thus, the central argument in favor of the use of legislative history is grounded in the purposivist view of legislative supremacy. 
By contrast, many textualists argue that legislative history should be used sparingly. The first and perhaps most persistent objection is theoretical: as Justice Scalia argued, the use of legislative history improperly "assumes that what [judges] are looking for is the intent of the legislature rather than the meaning of the statutory text." Accordingly, to the extent legislative history enables a judge to elevate a judgment about "background purposes" above "the clear import of an enacted text," textualists disagree with the use of this tool. Textualists frequently claim that using legislative history in this way is inappropriate because "as a formal matter," it is this text, and not the "committee reports and floor statements," that are "the law enacted by Congress." Textualists' primary objections to legislative history are therefore rooted in their own distinct view of how courts best observe legislative supremacy.
Many textualists also harbor more practical concerns about the reliability of legislative history. Justice Scalia has frequently argued that "[e]ven if legislative intent did exist, there would be little reason to think it might be found in the sources that the courts consult." Even committee reports do not necessarily represent the understanding of the full Congress, given that they are created by a minority of Members, making it dangerous to draw assumptions about the whole body's understanding of the statute from such documents, in the view of textualists. Justice Scalia also warned that legislative history is subject to intentional manipulation and gamesmanship, making it even less likely that these documents reflect legislative intent. Finally, judges have pointed out that due to the multiplicity of actors, "legislative history is often conflicting," making it difficult to determine which parts of the record should be heeded. Judge Harold Leventhal once observed that using legislative history can be like "looking over a crowd and picking out your friends." These concerns about the reliability of legislative history may apply whether the tool is used to discover a statute's purpose or for another reason. 
In light of these criticisms, judges who see value in examining legislative history to discern the legislature's intent have begun using such materials in more nuanced ways. Courts review legislative history in light of the text ultimately enacted, and in conjunction with other interpretive tools. Many judges also view some types of legislative history as more reliable than others, drawing from their understanding of congressional procedure. One group of prominent legal scholars created a hierarchy of legislative history derived from federal case law, shown in Figure 1 . Justice Sotomayor mirrored these views in a recent opinion, maintaining that committee reports "are a particularly reliable source" of legislative history because they are circulated with a bill to Members and their staff, and are viewed by those people as reliable indicators of the bill's meaning. By contrast, the Court has noted that floor debates are a weaker form of legislative history because they "reflect at best the understanding of individual Congressmen."
The preceding discussion does not account for a special form of legislative history—one that courts will generally presume holds significant weight in determining a statute's meaning: a history of amendment. Like the other forms of legislative history discussed in this report, legislative action amending a statute provides a record of congressional deliberation prior to the enactment of the disputed statute. However, unlike the other forms of legislative history, a prior version of a statute is itself formally enacted, and to many, therefore provides stronger evidence of a statute's evolution. The Supreme Court has said, "When Congress acts to amend a statute, we presume it intends its amendment to have real and substantial effect." As a result, a statute's amendment history can even overcome other evidence of statutory meaning.
section_title: Statutory Implementation
paragraphs: Finally, courts frequently investigate how a statute actually works, asking what problem Congress sought to address by enacting the disputed provision, and how Congress went about doing that. As a result, courts have assessed whether the consequences of an asserted interpretation align with the statutory scheme. Although a focus on practical consequences is, at least academically, most closely aligned with the so-called dynamic theories of interpretation and as such, is a generally disfavored view, scholars have maintained that "practical considerations play an important role in the [Supreme] Court's statutory cases." Courts sometimes look for such evidence in materials from the agencies that are charged with implementing the disputed statute, but they also rely on their own understandings of how the statute works.
subsections: section_title: Agency Interpretations
paragraphs: Administrative agencies are frequently the first official interpreters of statutes: in the course of implementing a statutory scheme, interpretive questions arise and must be resolved in order for the agency to do its work. When courts interpret a statute, they sometimes consider these agency interpretations, whether the agency's views are asserted through administrative rulings or a pattern of action. A judge might cite an agency's unofficial but public interpretation of a statutory term to support other evidence justifying a particular interpretation. Or a judge might use evidence of the way an administrative agency has implemented a statute to gain a sense of the problem that Congress sought to address and how the statutory scheme generally works to address that problem.
This use of an agency's interpretation of a statute is distinct from the special weight, called Chevron deference, that a court will sometimes give to an agency interpretation. Chevron deference generally applies when a court is reviewing an agency's official interpretation of a statute that the agency is charged with administering. In such a situation, if a statute is silent or ambiguous with respect to the specific issue being litigated, then Chevron instructs a court to give the agency's construction controlling weight, so long as it is reasonable. But courts will consider an agency's interpretation even when a court is determining for itself the best reading of the statute, outside the context of Chevron deference. Courts may view the agency's interpretation as evidence that the statute can bear a particular meaning, similar to a dictionary definition.
The legal scholars Hart and Sacks suggested that "popular" constructions of a statute, especially those embodied in the actions of those entities implementing that law, should be entitled to some special weight. According to Hart and Sacks, evidence of how a law has been implemented does not show merely "peoples' understanding of the [disputed] term . . . in the abstract," as a dictionary would, but gives "evidence of the understanding upon which people had acted ," and sometimes the ways in which people have acted against their own interests. In this sense, they contend that interpreters should give special weight to "action by the primary addressees who were required by the very nature of the arrangement to make the initial decisions under it." This view accords with one of the central justifications given for deferring to agency interpretations under Chevron : courts should give special weight to agency constructions of statutes that they administer because they have special expertise in that subject area, and because Congress itself, by charging the agency with implementation authority, has said that the agency has a special role in interpreting the statute. Notwithstanding these considerations, however, judges regularly reject agency interpretations if they are contrary to the text of the statute or other strong evidence of the statute's meaning.
section_title: Practical Consequences
paragraphs: Judges may also rely on their own understandings of how a statute should be implemented to interpret the statute's meaning. Even textualists, who generally protest the use of consequentialist reasoning, do regularly invoke policy consequences to evaluate the validity of a proffered interpretation. If a court believes that the practical consequences of a particular interpretation would undermine the purposes of the statute, the court may reject that reading even if it is the one that seems most consistent with the statutory text. Similarly, judges will refer to concerns of administrability when interpreting statutes. Judges may also rely on policy considerations to limit the reach of a statute, if one possible construction would seem to expand the government's authority beyond what the judge believes to be reasonable.
In one prominent example, the Supreme Court concluded in King v. Burwell that "the context and structure of the [Patient Protection and Affordable Care] Act compel us to depart from what would otherwise be the most natural reading of the pertinent statutory phrase." The disputed statutory provision provided that the availability of certain tax credits rested in part on whether a taxpayer had "enrolled in an insurance plan through 'an Exchange established by the State .'" At issue was whether these tax credits were "available in States that have a Federal Exchange rather than a State Exchange." The Court acknowledged that based solely on this statutory text, "it might seem that a Federal Exchange cannot fulfill [the] requirement" of being "established by the State." But, based on the statutory context and the "broader structure of the Act," the Court concluded that a strict textualist approach to interpreting the statute was not the best reading of the statute. The Court reviewed as a whole the reforms that the Act aimed to achieve and considered how the exchanges would actually operate under this plain-text reading. The Court noted that a reading that would deny tax credits to most individuals "could well push a State's individual insurance market into a death spiral." Ultimately, the Court decided that it was "implausible that Congress meant the Act to operate in this manner."
Justice Scalia authored the dissent in King , arguing that it was "quite absurd" to read "Exchange established by the State" to mean "Exchange established by the State or the Federal Government." Arguing that "[w]ords no longer have meaning if an Exchange that is not established by a State is 'established by the State,'" the dissent described the majority opinion as "rewriting the law under the pretense of interpreting it." The majority opinion itself recognized that "[r]eliance on context and structure in statutory interpretation is a 'subtle business, calling for great wariness lest what professes to be mere rendering becomes creation and attempted interpretation of legislation becomes legislation itself.'" But in the dispute before it, the Court argued, such reliance was warranted "to avoid the type of calamitous result that Congress plainly meant to avoid." The Court concluded by asserting that it was required to "respect the role of the Legislature, and take care not to undo what it has done." 
While King's discussion of an interpretation's practical consequences was quite obvious, courts may also consider the policy consequences of a particular interpretation in more subtle ways. Courts frequently will discuss pragmatic concerns in the context of a discussion of another interpretive tool. Many of the substantive canons, for instance, explicitly favor certain policy outcomes, inviting judges to choose the reading that comports with that outcome.
section_title: Developing Issues in Statutory Interpretation
subsections: section_title: Canons vs. Legislative History
paragraphs: The academic debate between purposivism and textualism is often framed in terms of the tools of interpretation that provoke the most debate. Broadly speaking, purposivists tend to advocate for the use of legislative history, while textualists are more likely to defend the canons of construction. As a result, the conventional wisdom pits purposivism and legislative history against textualism and the canons of construction. Recent scholarship has focused on the legitimacy of these tools and what the use of these tools says about the theoretical distinctions between the two camps.
As discussed above, both purposivist and textualist judges seek to act as faithful agents of the legislature, although in their search for statutory meaning, they both seek an objective legislative intent, rather than an actual one. There is broad consensus that a statute's text is primary, in that a court should start its interpretive task with the words of a statute and should also end there if the text is unambiguous. But courts frequently disagree about what types of context are fairly deemed inherent in that text and about which interpretive tools may help discover the context that is necessary to understand the statute's meaning. 
Purposivists argue that judges, in attempting to effectuate a statute's purpose, should attempt to figure out what Congress did, requiring a focus on legislative process. In their view, legislative history promises to illuminate this process, shedding light on what Congress sought to accomplish and how they went about doing that. The canons, by contrast, are judicially created, and not necessarily rooted in actual legislative processes. Thus, many purposivists believe that "reliable legislative history" acts as a better constraint than the canons to ensure that a court's decision reflects "what Congress had in mind," rather than a judge's own preferences.
Conversely, textualists maintain that judges, in focusing on a statute's text, should seek to figure out what Congress said, using the construct of ordinary meaning and drawing from the field of linguistics. Textualists doubt that judges have the capacity to determine a statute's purpose and, accordingly, seek to "develop effective rules of thumb to resolve the doubts that inevitably arise out of statutory language." The canons provide background rules for legislative drafting that are "traditional and hence anticipated." Thus, even if the canons do not reflect Congress's "actual" intent in a given case—and textualists doubt that such an intent is discoverable, if it even exists—textualists believe that the canons are nonetheless justified because they impose a greater constraint on a judge's discretion than does legislative history. 
This theoretical disagreement, as reflected in the use of legislative history versus canons of construction, may persist. However, a number of scholars have recently argued that this divide is not so stark as it appears—or, at least, that the choice to use legislative history or the canons may not neatly track judges' legal philosophies. In one empirical study of the Supreme Court's decisions issued between 2006 and 2012, the scholar Anita Krishnakumar concluded that "despite textualism's thirty-year-old campaign against legislative history . . . substantive canons have not displaced legislative history on the modern Supreme Court." She noted that while the use of legislative history had decreased since the era of the Burger Court, which ended in 1986, this overall decline in legislative history use was not accompanied by an equivalent increase in the use of the substantive canons. A distinct study from legal scholar Nina Mendelson of "the first ten years of the Roberts Court—October Terms 2005 to 2014," showed that all of the Justices "engaged very regularly" with both substantive and textual canons. This research indicates that even the Court's "conservative, textualist-leaning Justices" are still referencing legislative history, and the Court's more purposivist-leaning Justices are employing the canons of construction.
Another recent study surveyed federal appellate judges, asking them to describe their interpretive approaches and asking which tools of interpretation they use to decide cases. The authors of that study concluded that none of the judges surveyed could be characterized as "extreme" textualists or "extreme" purposivists. They found that all of the judges but one used legislative history, and all of the judges used the canons. Relying on this data, the authors argued that the assumption "that purposivist judges use legislative history, while textualist judges use canons . . . should be put to rest."
section_title: The Return of Actual Intent?
paragraphs: Legal scholarship has also called for the refinement of the tools described in this report. Some of the most prominent recent challenges from academia have asked whether the tools described above achieve the goals set for them—whether judges' conceptions of ordinary meaning in fact align with how people usually use language, whether the canons of construction reflect how Congress actually drafts statutes, and whether judges' use of legislative history reflects a proper understanding of how a bill is passed. Using empirical data, scholars have raised questions about whether judges can—or should—alter the way in which they use these tools to better adapt their interpretations to actual legislative intent. 
subsections: section_title: Linguistic Corpora
paragraphs: When judges explore a word's "ordinary meaning," they frequently revert to their own understandings of how they would use that word, in the context of the dispute before them. As a consequence, legal scholars have argued that the ordinary meaning construct is not as constraining as its defenders claim. Perhaps to defend against such charges, judges have cited dictionaries and other books as evidence of a word's ordinary meaning. But these books arguably provide evidence only that a word can be used to mean a certain thing, and do not necessarily prove conclusively that the suggested meaning is "ordinary," in the sense that it is commonly used in a specific context. That is, dictionaries demonstrate "the outer boundaries of appropriate usage," and any given dictionary might be more or less complete in distinguishing a term's "core meaning" from its "periphery."
Some scholars—and judges—have turned to corpus linguistics as a source of concrete data for determining the most common meanings of statutory phrases. "Corpus linguistics" uses large "collections of naturally occurring language called corpora" to study "language function and use." Courts can use these corpora to gather empirical evidence of "the common usage of a given term in a given context." For example, in Muscarello v. United States , the Supreme Court searched "computerized newspaper databases" to find sentences in which the disputed statutory terms appeared. At issue in that case was whether criminal defendants had "carrie[d]" a firearm by transporting it in a vehicle. The Court's search revealed that "many, perhaps more than one third" of the results were "sentences used to convey the meaning at issue here, i.e. , the carrying of guns in a car." For the majority of the Court, this provided solid evidence that this connotation of "carry"—to refer to a person carrying a gun in a car—was an "ordinary" use of the word.
Courts have also used an even more linguistically oriented database: the Corpus of Contemporary American English (COCA), "the largest freely-available corpus of English." Advocates drew evidence from COCA in arguments before the Supreme Court in the 2011 case of FCC v. AT&T , and some have argued that this linguistic evidence ultimately influenced the Court's opinion in that case. One state supreme court recently drew evidence from COCA to determine the meaning of the word "information." At issue was a statute that prohibited using "information" derived from certain statements of law enforcement officers against them in criminal proceedings, and the question before the court was whether the operative word should be interpreted to refer only to truthful information. The court concluded that the word "information" did not exclude false statements, noting that "empirical data from the COCA" showed that "[i]n common usage, 'information' is regularly used in conjunction with adjectives suggesting it may be both true and false." 
However, some have called for judges, who are not professional linguists, to be cautious in using these databases. Others have argued that using corpus linguistics may run contrary to standard judicial concerns about affording litigants notice. These notice concerns are enshrined in the ordinary meaning inquiry: by asking how an ordinary person would understand the statute, judges seek to ensure that this ordinary person had notice of the laws governing their conduct. Using corpus linguistics to determine how frequently newspapers or other periodicals have used a term in a certain way does not necessarily align with the understanding of the ordinary person, and can thus create notice concerns. Additionally, the databases themselves may have certain limitations that mean a particular meaning is absent from the corpus even though it is in fact a usual meaning of the word. Even those who generally defend the use of corpora note that they cannot definitely resolve the normative question of whether a particular meaning is "ordinary" in the context of the particular statute at issue.
section_title: Studies of Legislative Drafting
paragraphs: Other scholars have challenged various judicial assumptions about how Congress drafts statutes by conducting empirical studies of legislative drafting. As previously noted, most judges today try to act as faithful agents of the legislature when they interpret statutes, and they justify the interpretive tools they use along those terms. Some view canons as imitating the way Congress uses language and goes about achieving its policy goals. Likewise, others defend legislative history as revealing Congress's methods and purposes. Arguably then, if these tools do not reflect Congress's actual drafting practices, they are subject to attack on the basis that they do not help judges to act as Congress's faithful agents.
The most influential of recent studies on these issues was conducted by the scholars Abbe Gluck and Lisa Schultz Bressman, who surveyed 137 congressional staffers, mostly "committee counsels with drafting responsibility." They asked whether these drafters were aware of various judicial doctrines of statutory interpretation and whether the drafters actually complied with those doctrines. Their findings demonstrated a wide range of awareness and use of the various semantic and substantive canons. For instance, the authors found that legislative drafters were largely unaware of the canon of constitutional avoidance as a judicial presumption—but also discovered that the concept underlying the canon did in fact influence drafters, suggesting that the assumption that "Congress tries to legislate within constitutional bounds" is an accurate one. By contrast, the majority of staffers did know the canon against surplusage by name, but stated that this assumption is "rarely" accurate because drafters often "intentionally err on the side of redundancy."
Gluck and Bressman also asked these legislative drafters about many of the judicial assumptions underlying both the use and nonuse of legislative history. Their findings suggested that in contrast to some of the academic arguments against legislative history, both Members and their staff valued legislative history and believed that it "was an important tool for legislative drafters and courts alike." Further, they found that drafters believed that legislative history was a "tool that limited—rather than expanded—judicial discretion." The staffers also confirmed the judicial consensus that committee reports are generally the most reliable form of legislative history.
However, some have pointed out that Gluck and Bressman's study may not provide a complete view of the federal lawmaking process —and indeed, the authors themselves recognized many of the limitations in their study. As previously discussed, many judges, predominantly textualists, doubt whether courts are competent to understand the complicated processes that go into federal lawmaking. 
section_title: Empirical Data and Objective Intent
paragraphs: It remains to be seen whether these new empirical data will influence the way judges use well-established interpretive tools such as ordinary meaning, canons, and legislative history. In theory, both purposivism and textualism seek the most objectively reasonable meaning of a statute, rather than attempting to discern Congress's actual intent with respect to the question before the court. Purposivists ask what a reasonable legislator would have been trying to achieve by enacting this statute, while textualists ask what a reasonable English-speaker would have been trying to convey. By design, these theories are already removed from Congress's "actual intent." Accordingly, judges might conclude that evidence of actual practice, whether it is evidence from linguistic corpora of common usage, or evidence from congressional staffers of legislative drafting practices, is irrelevant.
But, as the reform-minded scholars have pointed out, if the way judges use various tools to construct statutory meaning is contrary to how Congress generally uses words or goes about achieving its policy goals, then using these tools undermines judges' claims that they are acting as Congress's faithful agents. Indeed, as noted above, judges have already begun to use linguistic corpora, as a source of empirical data, to refine the ways that they seek ordinary meaning. Similarly, judges have cited Gluck and Bressman's study to support the proposition that courts should give special weight to committee reports because of the evidence that committee staffers view them as reliable sources of legislative purpose. Other judges, including Justice Elena Kagan, have cited Gluck and Bressman's study to reject application of the canon against surplusage. In response to the new scholarship on statutory interpretation, one prominent textualist judge has suggested that courts should "shed" any semantic canons that do not in fact "reflect the meaning that people, including Members of Congress, ordinarily intend to communicate with their choice of words." Therefore, it is possible that further scholarship about actual legislative processes, and particularly legislative drafting practices, could affect the way that some judges read statutes. 
These studies may also reveal a need for Congress to learn more about how courts interpret statutes so that it can draft according to the prevailing interpretive conventions. However, as other scholars have pointed out, there are a number of other factors driving the federal drafting process, and it might not be feasible for Congress to make certain changes solely to cater to the courts. Nonetheless, because courts act as the arbiters of statutory meaning and necessarily shape the way a statute is implemented, Congress may be able to eliminate at least some misunderstandings by legislating with judges in mind. A continued dialogue between the courts and Congress can help ensure that laws are applied consistently with the intentions of the drafters.
subsections: section_title: Appendix. Canons of Construction
paragraphs: This appendix draws from two different works to present an exemplary list of the canons of construction. The two works take different approaches to compiling the canons, and sometimes disagree on what counts as a legitimate canon of construction. In their book Reading Law: The Interpretation of Legal Texts , Justice Antonin Scalia and Bryan Garner took an "unapologetically normative" approach to this task, collecting only those canons that they deemed valid under their approach to textualism. By contrast, a casebook authored by law professor William Eskridge and others took a more descriptive approach, compiling the canons "invoked by" the Supreme Court from 1986 to 2014. This appendix does not intend to stake out a position in any ongoing debates about the validity of the canons, and where feasible, notes disagreement among the authors.
Some editorial choices were made in the process of combining and reproducing the authors' lists. These edits include some generalization and consolidation of canons. The list also omits a number of canons that are too specific or otherwise outside the scope of this report, which aims to provide a general overview of how courts interpret statutes. The appendix likewise excludes canons that seem to represent substantive legal principles rather than assumptions about how to read statutes. 
This appendix names and briefly describes each canon, citing either or both of the two lists and applicable cases as appropriate. In many cases, the canon includes both the general rule and any relevant exceptions, in accord with the modern understanding that the application of a canon is highly context-dependent. The list distinguishes semantic canons from substantive canons, but does not further group the canons. The canons are listed in alphabetical order.
Semantic Canons
1. " Artificial-Person Canon ": "The word person includes corporations and other entities, but not the sovereign."
2. Casus Omissus : A matter not covered by a statute should be treated as intentionally omitted ( casus omissus pro omisso habendus est ).
3. " Conjunctive/Disjunctive Canon ": "And" usually "joins a conjunctive list," combining items, while "or" usually joins "a disjunctive list," denoting alternatives.
4. Ejusdem Generis : A general term that follows an enumerated list of more specific terms should be interpreted to cover only "matters similar to those specified."
5. Expresio Unius : "The expression of one thing implies the exclusion of others ( expressio unius est exclusio alterius )." This canon is strongest "when the items expressed are members of an 'associated group or series,' justifying the inference that items not mentioned were excluded by deliberate choice, not inadvertence."
6. " Gender/Number Canon ": Usually, "the masculine includes the feminine (and vice versa) and the singular includes the plural (and vice versa)."
7. " General/Specific Canon ": Where two laws conflict, "the specific governs the general ( generalia specialibus non derogant )." That is, "a precisely drawn, detailed statute pre-empts more general remedies," and conversely, "a statute dealing with a narrow, precise, and specific subject is not submerged by a later enacted statute covering a more generalized spectrum."
8. " General-Terms Canon ": "General terms are to be given their general meaning ( generalia verba sunt generaliter intelligenda )."
9. Grammar Canon : Statutes "follow accepted standards of grammar."
10. " Harmonious-Reading Canon ": "The provisions of a text should be interpreted in a way that renders them compatible, not contradictory."
11. " Irreconcilability Canon ": "If a text contains truly irreconcilable provisions at the same level of generality, and they have been simultaneously adopted, neither provision should be given effect." 
12. Legislative History Canons : "[C]lear evidence of congressional intent" gathered from legislative history "may illuminate ambiguous text." The most "authoritative source for finding the Legislature's intent lies in the Committee Reports on the bill." Floor statements, especially those made by a bill's sponsors prior to its passage, may be relevant, but should be used cautiously. "[T]he views of a subsequent Congress form a hazardous basis for inferring the intent of an earlier one."
13. " Mandatory/Permissive Canon ": "Shall" is usually mandatory and imposes a duty; "may" usually grants discretion.
14. " Nearest-Reasonable-Referent Canon ": "When the syntax involves something other than a parallel series of nouns or verbs, a prepositive or postpositive modifier normally applies only to the nearest reasonable referent."
15. Noscitur a Sociis : "Associated words bear on one another's meaning . . . ."
16. Ordinary Meaning Canon : Words should be given "their ordinary, everyday meanings," unless "Congress has provided a specific definition" or "the context indicates that they bear a technical sense."
17. Plain Meaning Rule and Absurdity Doctrine : "Follow the plain meaning of the statutory text, except when a textual plain meaning requires an absurd result or suggests a scrivener's error."
18. " Predicate-Act Canon ": "The law has long recognized that the '[a]uthorization of an act also authorizes a necessary predicate act.'"
19. " Prefatory-Materials " and " Titles-and-Headings " Canons : Preambles, purpose clauses, recitals, titles, and headings are all "permissible indicators of meaning," though they generally will not be dispositive.
20. Presumption of Consistent Usage : "Generally, identical words used in different parts of the same statute are . . . presumed to have the same meaning." Conversely, "a material variation in terms suggests a variation in meaning." 
21. " Presumption of Nonexclusive ' Include ' ": "[T]he term 'including' is not one of all-embracing definition, but connotes simply an illustrative application of the general principle."
22. " Presumption of Validity ": "An interpretation that validates outweighs one that invalidates ( ut res magis valeat quam pereat )." Stated another way, courts should construe statutes to have effect.
23. " Proviso Canon ": "A proviso," or "a clause that introduces a condition," traditionally by using the word "provided," "conditions the principal matter that it qualifies—almost always the matter immediately preceding."
24. Punctuation Canon : Statutes "follow accepted punctuation standards," and "[p]unctuation is a permissible indicator of meaning."
25. Purposive Construction : "[I]nterpret ambiguous statutes so as best to carry out their statutory purposes."
26. Reddendo Singula Singulis : "[W]ords and provisions are referred to their appropriate objects . . . ."
27. Rule Against Surplusage : Courts should "give effect, if possible, to every clause and word of a statute" so that "no clause is rendered 'superfluous, void, or insignificant.'"
28. Rule of the Last Antecedent : "[A] limiting clause or phrase . . . should ordinarily be read as modifying only the noun or phrase that it immediately follows . . . ."
29. " Scope-of-Subparts Canon ": "Material within an indented subpart relates only to that subpart; material contained in unindented text relates to all the following or preceding indented subparts."
30. Series-Qualifier Canon : "'When there is a straightforward, parallel construction that involves all nouns or verbs in a series,' a modifier at the end of the list 'normally applies to the entire series.'"
31. " Subordinating/Superordinating Canon ": "Subordinating language (signaled by subject to ) or superordinating language (signaled by notwithstanding or despite ) merely shows which provision prevails in the event of a clash—but does not necessarily denote a clash of provisions." 
32. " Unintelligibility Canon ": "[A] statute must be capable of construction and interpretation; otherwise it will be inoperative and void."
33. " Whole-Text Canon ": Courts "do not . . . construe statutory phrases in isolation; [they] read statutes as a whole."
Substantive Canons
1. Canon of Constitutional Avoidance : "[W]here an otherwise acceptable construction of a statute would raise serious constitutional problems, the Court will construe the statute to avoid such problems unless such construction is plainly contrary to the intent of Congress."
2. " Dog that Didn ' t Bark " Presumption : A "prior legal rule should be retained if no one in legislative deliberations even mentioned the rule or discussed any changes in the rule."
3. Federalism Canons : Courts will generally require a clear statement before finding that a federal statute "alter[s] the federal-state balance." Thus, for example, courts require Congress to speak with "unmistakeable clarity" in order to "abrogate state sovereign immunity." 
4. In Pari Materia : "[S]tatutes addressing the same subject matter generally should be read 'as if they were one law.'"
5. " Mens Rea Canon ": Courts should "presume that a criminal statute derived from the common law carries with it the requirement of a culpable mental state—even if no such limitation appears in the text—unless it is clear that the Legislature intended to impose strict liability." In the context of civil liability, "willfulness . . . cover[s] not only knowing violations of a standard, but reckless ones as well."
6. Nondelegation Doctrine : Courts should presume that "Congress does not delegate authority without sufficient guidelines."
7. " Penalty/Illegality Canon ": "[A] statute that penalizes an act makes it unlawful . . . ."
8. " Pending-Action Canon ": "When statutory law is altered during the pendency of a lawsuit, the courts at every level must apply the new law unless doing so would violate the presumption against retroactivity."
9. Presumption Against Extraterritoriality : Courts should presume, "absent a clear statement from Congress, that federal statutes do not apply outside the United States."
10. " Presumption Against Hiding Elephants in Mouseholes ": "Congress . . . does not alter the fundamental details of a regulatory scheme in vague terms or ancillary provisions—it does not, one might say, hide elephants in mouseholes."
11. Presumption Against Implied Repeals : "[R]epeals by implication are not favored."
12. Presumption Against Implied Right of Action : Courts should not imply a private remedy "unless . . . congressional intent [to create a private remedy] can be inferred from the language of the statute, the statutory structure, or some other source." Without such intent, "a cause of action does not exist."
13. Presumption Against Retroactive Legislation : "[C]ourts read laws as prospective in application unless Congress has unambiguously instructed retroactivity."
14. Presumption Against Waiver of Sovereign Immunity : A waiver of sovereign immunity "cannot be implied but must be unequivocally expressed." 
15. Presumption for Retaining the Common Law : "'[W]hen a statute covers an issue previously governed by the common law,' [courts] must presume that 'Congress intended to retain the substance of the common law.'"
16. Presumptions in Favor of Judicial Process : Courts sometimes require clear statements from Congress in order to bar judicial review of certain claims.
17. " Presumption of Continuity ": "Congress does not create discontinuities in legal rights and obligations without some clear statement."
18. Presumption of Legislative Acquiescence : "[A] long adhered to administrative interpretation dating from the legislative enactment, with no subsequent change having been made in the statute involved, raises a presumption of legislative acquiescence . . . ." This also applies to judicial interpretations of the statute. If Congress reenacts a statute without any change, it incorporates any settled judicial constructions of the statute "so broad and unquestioned that [a court] must presume Congress knew of and endorsed it . " However, "[o]rdinarily, . . . courts are slow to attribute significance to the failure of Congress to act on particular legislation."
19. Presumption of Narrow Construction of Exceptions : "An exception to a 'general statement of policy' is 'usually read . . . narrowly in order to preserve the primary operation of the provision.'"
20. " Presumption of Purposive Amendment ": Courts should assume that Congress intends any statutory "amendment to have real and substantial effect."
21. " Repeal-of-Repealer Canon ": "The repeal or expiration of a repealing statute does not reinstate the original statute."
22. " Repealability Canon ": "[O]ne legislature is competent to repeal any act which a former legislature was competent to pass; and . . . one legislature cannot abridge the powers of a succeeding legislature."
23. Rule of Lenity : "Ambiguity in a statute defining a crime or imposing a penalty should be resolved in the defendant's favor."