Major questions doctrine
The major questions doctrine is a relatively new principle of statutory interpretation applied in United States administrative law cases which states that courts will presume that Congress does not delegate to executive agencies issues of major political or economic significance. According to retired D.C. Circuit Judge Thomas Griffith and Haley Proctor, the "seminal statement" of the major questions doctrine comes from FDA v. Brown & Williamson Tobacco Corp. (2000): "[W]e must be guided to a degree by common sense as to the manner in which Congress is likely to delegate a policy decision of such economic and political magnitude to an administrative agency." There are at least two versions of the doctrine, a narrow version (a limitation on Chevron deference) and a broad version (a clear statement rule). Under the narrow version, the doctrine serves only to say that, when an agency asserts that it has authority to decide major questions, courts should independently determine whether the agency's interpretation of its statutory authority is the most reasonable reading of the statute. Under the broad version, the doctrine says that courts must not interpret statutes as delegating major questions to agencies unless Congress clearly said so. Chief Justice John Roberts summarized the major questions doctrine in the landmark case of West Virginia v. Environmental Protection Agency (2022) as follows:

In the years since the Supreme Court adopted the broader version of the major questions doctrine, legal scholars have criticized the doctrine along various lines. These include arguments that the major questions doctrine is a symptom of "judicial self-aggrandizement," that it is inconsistent with both textualism and originalism, and that it is at odds with normal tools of statutory interpretation. In an article for the Harvard Law Review summarizing this transformation in the major questions case law, Professor Mila Sohoni wrote that the "first crucial thing to understand about the major questions [doctrine] is what it did to administrative law." She continued, "[w]hile ostensibly applying existing major questions case law, the [Supreme Court] in actuality altered the doctrine of judicial review of agency action in its method and content, in ways that will have momentous consequences." As a limitation on Chevron deference 
The narrower version of the major questions doctrine is as an exception to Chevron deference. Under Chevron v. Natural Resources Defense Council (1984), courts defer to reasonable agency interpretations of ambiguous provisions:

Chevron treats Congressional silence or ambiguity in a statute as an implicit delegation of authority to the agency entrusted to implement the statute. Since MCI Telecommunications Corp. v. AT&T Co. (1994), the Supreme Court has occasionally declined to give agencies deference in several cases where it did not think Congress would grant sweeping authority in seemingly insignificant provisions. In 1986, Stephen Breyer, at the time a judge on the First Circuit, endorsed a narrow, flexible version of the major question doctrine in a law review article in 1986, two years after Chevron. Breyer's article also coined the phrase "major questions." After joining the Supreme Court in 1994, Breyer dissented in several major question cases, and was critical of the doctrine's expansion. As a clear statement rule 

The broad version of the major questions doctrine is a clear statement rule, saying that statutes must not be interpreted as delegating power to decide major questions unless the text clearly grants such power. The Supreme Court moved toward this approach in West Virginia v. EPA (2022), though previous cases also pointed toward a clear-statement approach. In Utility Air Regulatory Group v. Environmental Protection Agency (2014), the Court stated that "[w]e expect Congress to speak clearly if it wishes to assign to an agency decisions of vast 'economic and political significance.'" In West Virginia, the majority did not explicitly refer to its test as a "clear statement rule," but did refer multiple times to looking for "clear congressional authorization" (quoting UARG). In four cases, from Alabama Association of Realtors v. HHS (2021) to West Virginia v. EPA (2022), the Court "adopt[ed] a different and more potent variant of the 'major questions' exception," separate from Chevron deference. Before joining the Supreme Court, Brett Kavanaugh, then a judge on the D.C. Circuit, endorsed a broad interpretation of the major questions doctrine as a constitutional limitation on agency power in 2017 in a dissent in U.S. Telecom Association v. FCC, saying that "[t]he major rules doctrine helps preserve the separation of powers and operates as a vital check on expansive and aggressive assertions of executive authority." In Gundy v. United States (2019), a case which did not actually involve the major questions doctrine, Justice Gorsuch noted in dissent (joined by Roberts and Thomas) that "[a]lthough it is nominally a canon of statutory construction, we apply the major questions doctrine in service of the constitutional rule that Congress may not divest itself of its legislative power by transferring that power to an executive agency." Gorsuch reiterated this justification for the doctrine as a clear-statement rule in his concurrence in West Virginia (joined by Alito). "Elephants in mouseholes" 
The major questions doctrine is sometimes referred to as (or distinguished from) the elephants in mouseholes principle (or doctrine, canon, etc. ), based upon the aphorism of Justice Scalia's majority opinion in Whitman v. American Trucking Associations, Inc. (2001) that 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." Significant cases 
 In Interstate Commerce Commission v. Cincinnati, New Orleans & Texas Pacific Railway Co. (1897), the Court held that Congress had not given the Interstate Commerce Commission authority to fix prices. The Court stated that 

 In MCI Telecommunications Corp. v. AT&T Co. (1994), Justice Scalia wrote the decision of the Court rejecting an effort by the Federal Communications Commission to deregulate prices charged by common carriers. Even though the Communications Act required common carriers to file "tariffs" setting fixed prices for their service, the FCC relied on a provision allowing it to "modify any requirement" in order to make this requirement optional. The Court held that statutory authorization to "modify" refers only to smaller changes, and does not extend to setting aside entirely such a significant statutory mandate. The dissenting justices would have upheld the FCC's deregulatory interpretation under Chevron. In FDA v. Brown & Williamson Tobacco Corp. (2000), Justice O'Connor wrote that the authority of the Food and Drug Administration to regulate "drugs" or "devices" did not extend to regulating cigarettes and tobacco, relying in part on "common sense as to the manner in which Congress is likely to delegate a policy decision of such economic and political magnitude to an administrative agency" (citing MCI v. AT&T). The Court noted that if the FDA's interpretation were correct, then the FDA would have a duty to prohibit cigarettes entirely (because they are unsafe and non-therapeutic devices). In Whitman v. American Trucking Associations, Inc. (2001), a decision holding that Congress unambiguously directed the Environmental Protection Agency to set NAAQS clean air standards without considering costs, Justice Scalia wrote for the Court that "Congress, we have held, 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." In Gonzales v. Oregon (2006), the Court held that the Attorney General did not have authority under the Controlled Substances Act to prohibit doctors from prescribing regulated drugs for use in physician-assisted suicide where allowed by state law. A.G. Alberto Gonzales had relied on a statutory provision allowing him to revoke a physician's prescription-drug registration when "inconsistent with the public interest." Writing for the majority, Justice Kennedy said that "[t]he importance of the issue of physician-assisted suicide, which has been the subject of an 'earnest and profound debate' across the country, [Washington v. Glucksberg], 521 U.S., at 735, makes the oblique form of the claimed delegation all the more suspect." In Utility Air Regulatory Group v. Environmental Protection Agency (2014), the Court held that, for purposes of a portion of the Clean Air Act regulating "small sources," the phrase "air pollutants" did not extend to carbon dioxide. Even though the Court had held in Massachusetts v. EPA (2007) that "air pollutants" as used in another section of the statute included carbon dioxide, a majority in UARG v. EPA rejected that same interpretation because it would allow EPA to regulate "the operation of millions[] of small sources nationwide" including "large office and residential buildings, hotels, large retail establishments, and similar facilities." Because of that, the Court said that it would first expect Congress to speak clearly before sweeping in such a broad swath of the American economy. In King v. Burwell (2015), a case interpreting the Affordable Care Act, the decision of Chief Justice Roberts declined to apply Chevron deference based on the major questions doctrine. The statute, which gives subsidies to insurance plans bought on exchanges "established by the State," was interpreted by the Department of Health and Human Services to also apply to an exchange established by the federal government. HHS relied in part on Chevron deference to support its interpretation, but the Court said that the agency was not entitled to deference. And even though the Court stated that "the most natural reading of the pertinent statutory phrase" went against HHS, nevertheless the Court agreed that HHS's reading was the correct one based on the larger statutory scheme. In Alabama Assn. of Realtors v. Department of Health and Human Servs. (2021) (per curiam), the Court concluded that the Centers for Disease Control and Prevention (CDC) could not institute a nationwide eviction moratorium under its authority to adopt measures “necessary to prevent the [...] spread of” disease. The decision also noted that "[t]he moratorium intrudes into an area that is the particular domain of state law: the landlord-tenant relationship" and that "'[o]ur precedents require Congress to enact exceedingly clear language if it wishes to significantly alter the balance between federal and state power and the power of the Government over private property'" (quoting U.S. Forest Service v. v. Cowpasture River Preservation Assn. (2020)). Biden v. Missouri (2022) (per curiam)

 National Federation of Independent Business v. Department of Labor, Occupational Safety and Health Administration (2022) (per curiam)

 In West Virginia v. EPA (2022), the Supreme Court held, in a decision by Chief Justice Roberts that the phrase "best system of emission reduction [...] adequately demonstrated" (BSER) in section 111 of the Clean Air Act () did not allow EPA to set emissions standards based on phasing out coal or natural gas, but rather only based on techniques to improve efficiency within each type of energy generation. The Court said that this "generation shifting" approach (rather than a "technology-based approach"), adopted for the first time in the 2015 Clean Power Plan, was an "unheralded power" and "transformative expansion" of the agency's "regulatory authority" found in an "ancillary provision" "that was designed to function as a gap filler and had rarely been used in the preceding decades" in order "to adopt a regulatory program that Congress had conspicuously and repeatedly declined to enact itself" that "essentially adopted a cap-and-trade scheme, or set of state cap-and-trade schemes, for carbon" and would allow "unprecedented power over American industry." Accordingly, the Court concluded that the EPA would have needed “clear congressional authorization” to overcome the Court's skepticism that Congress would have legislated in such a manner. In Biden v. Nebraska (2023), the Court relied in part on the major questions doctrine in its holding that Congress did not authorize the Department of Education to institute a sweeping student loan forgiveness program under the HEROES Act of 2003. Justice Barrett also filed a concurring opinion specifically devoted to analyzing the doctrine and its origins. She argued that it is not a clear statement rule in tension with textualism but rather a contextual and intuitive linguistic canon for determining the plain meaning of a statute. See also 
 Nondelegation doctrine

Notes

References 

United States administrative law
Legal doctrines and principles