Article Correction for the 51-49 Rule of Constitutional and Statutory Interpretation; Loper Bright and Interpreting Out Ambiguity (11/9/26)

I write this blog to add nuance, dialing back a key claim I made in my article Loper Bright Flip Flops on Chevron Deference: A Tax Lawyer's Perspective, 79 Tax Law. 323 (2026), here. In broad strokes, I questioned whether Loper Bright’s claims about the state of the law at the enactment of the APA in 1946, noting particularly the role of a famous tax case, Dobson v. Commissioner, 320 U.S. 489 (1943) that Loper Bright ignores and the statutory text interpreted in Dobson. I do not change that discussion. More importantly for this blog, I questioned Loper Bright’s claims that

(i) Chevron required courts to defer to an agency interpretation over an interpretation that they determined to be the best interpretation; and

(ii) through rigorous interpretation, courts can interpret out interpretive ambiguity (aka interpretive equipoise) where a court could not determine with sufficient confidence which of two competing interpretations was the best interpretation.

I do not change (i) in any respect.

I add considerable nuance to (ii).

Focusing on (ii), I posited that courts honest with themselves would sometimes encounter interpretive issues that would not permit a best interpretation with sufficient confidence and, in that state which I posited as a range, the court would either (a) need a default tool to decide the issue (such as Chevron provided prior to Loper Bright and other interpretive tools (such as lenity) in other contexts) or (b) use some other nonprincipled method (such as flipping coins or going with the court’s policy preferences) to break the tie. (I called that process “law-finding” like fact-finding.) I said (pp. 338-339) using a more likely than not standard for legal interpretation (remember that standard for law-finding in the penalty for tax shelters?):

More likely than not is often conceptualized as at least 51%–49%, with 50%–50% being a state of interpretive equipoise where one cannot determine probability one way or the other. Even that acknowledges a range of equipoise from 49.0001% to 50.9999%. In any event, how can anyone make a meaningful distinction between a 51% interpretation and a 49% interpretation? If (as I think) that cannot be done in any meaningful way, then legal interpretive equipoise involves a range of reasonable interpretations, say of 55% and 45% or 60% and 40% or even some larger spread.n58 If that is right, then a lawyer’s opinion or a court opinion will have to treat the range as being a state of interpretive equipoise where the “best” and “not best” interpretations cannot be determined.
   n58 See Kavanaugh, supra note 48. See also Ryan Doefler, How Clear Is Clear?, 198 VA. L. REV. 651, 682 (2023) (on the motivated reasoning affecting interpretive outcomes stating: 
In an ordinary statutory case, a judge could, without embarrassing herself, mischaracterize a merely likely interpretation as “unlikely.” And because it is an ordinary case— that is, a case in which the evidentiary threshold is more likely than not—that would be enough to alter the outcome. Here, again, the question is why think that judges would have an easier time exaggerating or understating the likelihood of various readings if the epistemic threshold were, say, 65-35, as opposed to 51-49? In any statutory case, there must be some line past which the moving party prevails. And wherever that line happens to be, the risk of willfulness or motivated reasoning will be greater the closer a case is to that line.

See also my article pp. 345-349 where I say that Loper Bright’s claim of no ambiguity/equipoise is a legal fiction much in the way that Chevron’s claim of interpretation from ambiguity permitted a presumption of interpretive authority.

I subsequently reviewed and commented in a blog on an article where, in comments to my blog entry, the author and I discussed my range of ambiguity/equipoise argument. Comments on Highly Recommended Article Extending Skidmore "Deference" Approved in Loper Bright (Federal Tax Procedure Blog 3/7/26; 3/8/26), here. The author, Mitchell Zaic, argued (highly summarized) that, under Loper Bright, equipoise would be encountered only at 50%-50% level of confidence, meaning (again highly summarized) that 51%-49% confidence level requires the judge to apply the 51% interpretation. Mr. Zaic disagreed with my thesis that a judge cannot make a meaningful determination that a 51% confidence level is better than the 49% interpretation. (Of course, even that argument says there is a range of ambiguity between 51% and 49%; but as a practical matter most would say that anything in that constricted range was 50-50.)

I have recently read two articles that develop the “51-49 rule” in constitutional interpretation, an exercise that is not materially different from statutory interpretation. Aaron Tang, Second-Order Constitutional Theory, 93 U. Chi. L. Rev. 1447 (2026), here; and John O. McGinnis & Michael B. Rappaport, The Constitution's Own Interpretive Method: Advancing the Original Methods Approach, 102 Notre Dame L. Rev. (forthcoming 2027) (SSRN here).

I start with Professor Tang’s article. Professor Tang categorizes constitutional interpretation as involving first-order process, meaning applying the interpreter’s preferred constitutional interpretation method (originalism, pragmatism, even textualism, etc.), and then if first-order process does not resolve ambiguity, applying a second-order process to resolve ambiguity and decide the case. Professor Tang devotes (pp. 1467-1478) a significant portion of the article to listing and discussing “Some Common Second-Order Theories” used by the Supreme Court to resolve first-order uncertainty. This uncertainty after first-order process (the method of interpretation) basically parallels my argument of ambiguity or equipoise. Second-order processes resolve the ambiguity or equipoise in the way Chevron deference did; indeed in this regard, one of the second order processes Professor Tang discusses (pp. 1471-1474) is “Legislative Deference.”

First up on Professor Tang’s list of Common Second-Order Theories is “The 51-49 rule” (pp. 1467-1471). Professor Tang describes it:

The most common second-order approach to resolving legal uncertainty is so familiar as to be unstated: rule in favor of whichever answer has more evidence to support it than any other. Professor Gary Lawson has written the most important and comprehensive descriptive account of this default rule, which he calls the “best-available-alternative” standard: In difficult cases, courts typically adopt the constitutional interpretation that is better than all other options, no matter how close or uncertain the evidence.n109
   n109 LAWSON, EVIDENCE OF THE LAW, supra note 40, at 202–03; see also Gary Lawson, No History, No Certainty, No Legitimacy . . . No Problem: Originalism and the Limits of Legal Theory, 64 FLA. L. REV. 1551, 1561–63 (2012); Gary Lawson, Proving the Law, 86 NW. U. L. REV. 859, 890–91 (1992).

The process as described by Professors Lawson and Tang involves law-finding like fact-finding where the party having the affirmative of the legal interpretation (i.e., must convince the court of the legal interpretation) to prevail. I will further address burden of proof in law-finding in this context at the end of this blog.

Professor Tang says that the label “51-49 rule” was not Lawson’s but the label of “fellow originalists McGinnis and Rappaport” the authors of the second article I cite and link above, who describe the rule as requiring the interpreter to choose “the better interpretation of a provision, even if it is only slightly better,” with Professor Tang elaborating in footnote 111 on p. 1468:

This 51–49 rule, they [Professor McGinnis & Rappaport] argue, is “a key to reducing uncertainty” about the Constitution— and they argue that it is called for by the Constitution itself. Id. I return to the second claim below. See infra Part II.B.3. I note now, though, that the 51–49 rule does not “reduc[e] uncertainty” about the Constitution in a strict sense; it is not, in other words, a first-order tool that would allow a legal thinker to become more confident that a given constitutional interpretation is the correct one. Instead, the rule is better thought of as a tool for deciding a constitutional question in the face of uncertainty when people could reasonably reach different conclusions as to which outcome possesses 51% of the relevant evidence.

Professor Tang says (pp. 1468-1469) that the 51-49 “naming convention * * * efficiently captures the rule’s distinctive feature: When the relevant body of evidence points in competing directions, choose the outcome that has more evidence to support it, however marginal the difference.”

So how is this relevant to statutory interpretation which is the domain of Loper Bright? Professor Tang says (p. 1471 n. 124) , correctly I think,

Or consider the Court’s recent embrace of what is effectively the 51–49 rule in the related context of statutory interpretation, where it rejected the longstanding second-order rule of Chevron deference to agencies and instead directed judges to “use every tool at their disposal to determine the best reading of [an ambiguous] statute.”n124
   n124 Loper Bright Enters. v. Raimondo, 144 S. Ct. 2244, 2266 (2024) (emphasis added). Indeed, this Article’s distinction between first- and second-order theories of constitutional adjudication could apply with similar conceptual force to the development of a fully worked-out approach to statutory interpretation.

My key point about the 51-49 rule is that, from my perspective, the 51-49 rule for  marginal differences unresolved by first-order processes does not permit principled resolution of the interpretive issue. Yet it appears that mainstream analysis may be more consistent with Mr. Zaic’s interpretation of the process required by Loper Bright. However, I stick by my conclusion that this genre of marginal differences do not permit principled resolution of the interpretive issue because the judge finding the interpretations at 51-49 cannot articulate a reason that 51 prevails over 49; the judge will not say that he flipped a coin or use some other arbitrary process (including his own policy preferences) to decide the case.

Professor McGinnis and Rappoport’s new article (cited and linked above) is similar, describing (p. 108) the 51-49 rule as instructing “interpreters to select the better interpretation, even if it is only marginally better than the alternative reading. Under this framework, instances of true indeterminacy, such as those involving irreducibly vague terms, are rare; when they do arise, they concern borderline issues of secondary importance.”

I said I would return to the use of burden of proof concepts with respect to statutory interpretation, a law-finding exercise rather than a fact-finding exercise. In his concluding discussion of Some Common Second-Order Theories, Professor Tang says (pp. 1477-1478):

To summarize, each of the leading second-order theories entails two elements: a burden of proof and a decision rule for what to do if that burden is not satisfied. Sometimes the burden of proof is articulated in qualitative terms—such as the Thayerian requirement of proof of a constitutional violation that is “clear” or “beyond a reasonable doubt.” The 51–49 rule, by contrast, is quantitative. Sometimes the requisite burden of proof is unspoken; sometimes it is the subject of open contestation. Importantly, what these differing proof thresholds reflect is competing values and individual attitudes, not some objective empirical truth in the world about when first-order uncertainty is too great to tolerate.