We often think of the Constitution as a two-part document: first the original 1787 text, which primarily establishes the government’s structure; and then the amendments, which primarily set forth our rights. But it’s not nearly that simple: Our government’s structure—its federalism and its separation of powers—was devised not just to promote energetic government, but also to secure individual liberty. Or, as Alexander Hamilton stressed in Federalist 84, “the truth is” that the original structural Constitution “is itself, in every rational sense, and to every useful purpose, a bill of rights.”

In recent years, the relationship between structure and rights has been emphasized by Justice Anthony Kennedy. And his comments at oral argument in Sebelius v. Hobby Lobby, the case challenging the Department of Health and Human Services’ “contraception mandate” on religious liberty grounds, suggest that he may be returning to that theme once again.

Because Justice Kennedy occupies the Court’s ideo-logical and tactical center, lawyers and pundits invest great effort in analyzing where he might land in any given case. In 2011 and 2012, as the constitutional challenge to Obamacare’s individual mandate made its way to the Court, all were focused on Justice Kennedy’s well-established habit of invoking the commerce clause, which divides power between the federal and state governments, as a bulwark of liberty.

Specifically, observers turned to Kennedy’s separate opinion in United States v. Lopez (1995). In that case, the Rehnquist Court held that the commerce clause did not empower Congress to regulate guns unconnected to interstate commerce. But Kennedy also wrote separately to stress that, “though on the surface the idea may seem counterintuitive, it was the insight of the Framers that freedom was enhanced by the creation of two governments, not one.” He continued by quoting James Madison’sFederalist 51:

In the compound republic of America, the power surrendered by the people is first divided between two distinct governments, and then the portion allotted to each subdivided among distinct and separate departments. Hence a double security arises to the rights of the people. The different governments will control each other, at the same time that each will be controlled by itself.

Kennedy reiterated these federalist themes in Bond v. United States (2011), this time writing for the majority to explain why an individual had “standing” to vindicate the states’ commerce clause interests in court. Again invoking Madison, he stressed, “Federalism has more than one dynamic.” While “the federal structure serves to grant and delimit the prerogatives and responsibilities of the States and the National Government vis-à-vis one another,” federalism protects more than just the respective domains of our national and state governments. “Rather, federalism secures to citizens the liberties that derive from the diffusion of sovereign power.”

And so a year later, when the Supreme Court decided the Obamacare individual mandate case, these federalist themes were central to the conservative justices’ opinion that the mandate exceeded the limits of the commerce clause. While the opinion was signed jointly by Kennedy, Scalia, Thomas, and Alito, the distinctive tones of Kennedy’s previous opinions rang clearly: “Structural protections—notably, the restraints imposed by federalism and separation of powers—are less romantic and have less obvious a connection to personal freedom than the provisions of the Bill of Rights or the Civil War Amendments,” the justices observed. But “the Framers considered structural protections of freedom the most important ones, for which reason they alone were embodied in the original Constitution and not left to later amendment. The fragmentation of power produced by the structure of our Government is central to liberty, and when we destroy it, we place liberty at peril.”

Even more recently, Justice Kennedy commingled notions of federalism and individual liberty in his opinion for the Court in Windsor v. United States (2013), striking down the Defense of Marriage Act’s federal definition of marriage. There, Kennedy held that the federal government’s denial of recognition for same-sex marriages violated the Fifth Amendment’s due process (and implicit equal protection) clause, but only after reading the Fifth Amendment against the background of traditional state authority, rather than federal authority, to define marriage.

Again, Justice Kennedy’s habit of connecting federalism to liberty is by now so well established that it borders on conventional wisdom. But Madison’s famous words inFederalist 51 were not limited to federalism. Madison saw liberty protected not just by the division of power between the national and federal governments, but also in the division of power, within the national government, “among distinct and separate departments”—or, the separation of powers among the legislative, executive, and judicial branches, which ensures that the national government “will be controlled by itself.”

This second structural protection seems to be on Justice Kennedy’s mind, and in the latest constitutional case involving Obamacare, no less. But Justice Kennedy’s allusions to this constitutional theme, at recent oral arguments, have gone largely unnoticed.

In Sebelius v. Hobby Lobby, the Hobby Lobby arts-and-crafts company argues that the Health and Human Services Department’s “contraception mandate” violates the company’s (and its owners’) right to freely exercise religion. Their claims are rooted in the First Amendment’s fundamental protections, but they are more immediately protected by the Religious Freedom Restoration Act, a 1993 statute that provides that generally applicable federal laws should not be enforced in a way that would “substantially burden a person’s exercise of religion,” unless the law is the “least restrictive means of furthering” a “compelling government interest.”

In the run-up to the Hobby Lobby case, most discussion focused on questions of whether corporations actually have free-exercise rights, or whether HHS’s regulations truly burden those rights to an unlawful degree. But at oral argument, as legal writers Ed Whelan and Josh Blackman noted, Justice Kennedy seemed keenly interested in questions of constitutional structure. This time, his questions went not to the allocation of power between the federal government and the states, but the allocation of power among Congress and the executive branch.

Congress did not impose the contraception mandate on employers; the administration did. The Affordable Care Act directs large employers only to provide employees the opportunity to enroll in “minimum essential coverage,” pursuant to HHS’s implementation of the act. And so, with Solicitor General Donald Verrilli at the podium, Kennedy stressed the fact that this collision between Obama-care and religious liberty arose not because the statute itself forced HHS’s hand, but because HHS itself had used a vague statute to force the constitutional issue:

Now, what—what kind of constitutional structure do we have if the Congress can give an agency the power to grant or not grant a religious exemption based on what the agency determined? I recognize delegation of powers rules are somewhat more abundant insofar as their enforcement in this Court. But when we have a First Amendment issue of this consequence, shouldn’t we indicate that it’s for the Congress, not the agency, to determine that this corporation gets the exemption on that one, and not even for RFRA purposes, for other purposes?

By mentioning “delegation,” Justice Kennedy seemed to allude to the “nondelegation doctrine,” a longstanding principle of constitutional structure rooted in Article I, Section 1 of the Constitution. That provision vests Congress, and Congress alone, with “all legislative powers” granted to the national government. Thus, the nondelegation doctrine, as developed by the courts, prohibits Congress from “delegating” its legislative power to any agency.

It is not a doctrine that lends itself easily to bright-line standards—as Justice Scalia has observed, “the debate over unconstitutional delegation becomes a debate not over a point of principle but over a question of degree.” In practice, as seen in the Court’s precedents, the nondelegation doctrine requires only that Congress specify an “intelligible principle” to guide and limit the agency that applies Congress’s enactment.

In fact, Kennedy’s allusion to “delegation” may have surprised observers, if only because the Court has so rarely invoked the doctrine to strike down statutes. As the Court itself noted in 2001, only twice in the nation’s entire history has the Court used the doctrine to strike down a federal statute—both times in 1935. Or, as Cass Sunstein, a law professor and former Obama White House official, wrote in 2000, “We might say that the conventional doctrine has had one good year, and 211 bad ones (and counting).”

But while the nondelegation doctrine only rarely causes a court to strike down a statute completely, the doctrine can play a substantial role in how the courts interpret statutes. As Sunstein wrote in his influential article,

But is the nondelegation doctrine really dead? On the contrary, I believe that the doctrine is alive and well. It has been relocated rather than abandoned. Federal courts commonly vindicate not a general nondelegation doctrine, but a series of more specific and smaller, though quite important, nondelegation doctrines. Rather than invalidating federal legislation as excessively open-ended, courts hold that federal administrative agencies may not engage in certain activities unless and until Congress has expressly authorized them to do so. The relevant choices must be made legislatively rather than bureaucratically.

In short, the nondelegation doctrine offers a fundamental principle to guide courts in the work of interpreting statutes. Congress often writes statutes in very broad terms, leaving substantial room for willful agencies to make major policy decisions. Delegating too much discretion to an agency would undermine the Framers’ basic vision, stated best by Madison in Federalist 51, that legislative and executive power must be kept separate, so that the national government “will be controlled by itself.” Thus, when a court is called upon to review an agency’s implementation of a statute, the nondelegation doctrine reminds that it may be necessary for the court to construe the statute somewhat more narrowly, to vindicate the Constitution’s separation of powers.

But the nondelegation doctrine differs slightly from more common separation-of-powers questions. Usually, the separation of powers is intended to guard against the risk that one branch will encroach upon the powers of the other. But sometimes the problem is not that a branch wants too much power, but too little—that is, the branch wants to avoid responsibility for its own actions. Thus, the nondelegation doctrine ensures Congress’s accountability, by preventing Congress from blithely handing to agencies the power to make important policy choices that ought to be decided by Congress in the first instance.

In the federal courts, that point has been made eloquently by .  .  . Justice Kennedy, in a series of opinions that have attracted nowhere near the attention that his federalism opinions attracted. Indeed, he made this point long before his appointment to the Supreme Court. In 1981, when he was still a judge on the U.S. Court of Appeals for the Ninth Circuit, Kennedy heard the case of Chadha v. INS, challenging the constitutionality of a federal law empowering each house of Congress to veto decisions by the Immigration and Naturalization Service not to deport aliens. Kennedy and two other judges unanimously ruled that the “one-house veto” violated the Constitution’s separation of powers. (The Supreme Court later affirmed their ruling, in a seminal separation-of-powers decision.)

Kennedy’s opinion for the Ninth Circuit focused primarily on the dangers of Congress encroaching upon the president’s exclusive power to execute the laws, but he also examined the issue from the other direction, in terms of delegation and responsibility:

The concern for the autonomy of each branch is shown by a corollary of the separation doctrine, namely, the rule against undue delegation of powers. Just as the separation of powers prohibits the accumulation of too much power in one branch, the nondelegation doctrine prevents one branch from abrogating its authority in a wholesale and standardless manner.

As Kennedy explained, the separation of powers among the branches and the nondelegation doctrine ultimately serve two distinct interests: the “twin purposes” of “promoting governmental efficiency” and “preventing concentrations of power dangerous to liberty.”

Once elevated to the Supreme Court, Kennedy has returned time and time again to the role of the Constitution’s separation of powers as a structural protection for liberty, just as he returned to the relationship between federalism and liberty. In Public Citizen v. Department of Justice (1989), a case asking whether Congress could pass statutes affecting the president’s power to nominate judges, Justice Kennedy’s concurring opinion opened with a strong defense of the separation of powers in service of liberty, quoting first Charles Pinckney and then Madison’s Federalist Papers:

“In a government, where the liberties of the people are to be preserved .  .  . , the executive, legislative and judicial, should ever be separate and distinct, and consist of parts, mutually forming a check upon each other.”

The Framers of our Government knew that the most precious of liberties could remain secure only if they created a structure of Government based on a permanent separation of powers. See, e.g., The Federalist Nos. 47-51 (J. Madison). Indeed, the Framers devoted almost the whole of their attention at the Constitutional Convention to the creation of a secure and enduring structure for the new Government. It remains one of the most vital functions of this Court to police with care the separation of the governing powers. That is so even when, as is the case here, no immediate threat to liberty is apparent. When structure fails, liberty is always in peril.

Justice Kennedy struck similar notes in his concurring opinion in the line item veto case, Clinton v. City of New York (1998) (“Liberty is always at stake when one or more of the branches seek to transgress the separation of powers”), and in his opinion for the Court in one of the Guantánamo detention cases, Boumediene v. Bush (2008) (“The Framers’ inherent distrust of governmental power was the driving force behind the constitutional plan that allocated powers among three independent branches. This design serves not only to make Government accountable but also to secure individual liberty”).

But on questions of Congress delegating power to agencies, Kennedy’s focus on liberty is most clearly pronounced in his opinion for the Court in Gonzales v. Oregon(2006). There the government argued that because the Controlled Substances Act (CSA) empowers the attorney general to regulate or prohibit the distribution of drugs, the attorney general could prohibit the distribution of drugs for physician-assisted suicide. But Justice Kennedy, writing for the Court majority, rejected the suggestion that the CSA’s grant of general regulatory power to the attorney general could be construed as empowering him to decide unilaterally the contentious issue of assisted suicide. The “idea that Congress gave the Attorney General such a broad and unusual authority through an implicit delegation,” Kennedy wrote for the Court, “is not sustainable.” Quoting key precedents on these themes, Kennedy stressed 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.” The Court will not casually affirm an agency’s constitutionally controversial assertions of regulatory power, precisely because the Court is “confident that Congress could not have intended to delegate a decision of such economic and political significance to an agency in so cryptic a fashion.”

When the issue of physician-assisted suicide had been “the subject of an ‘earnest and profound debate’ across the country,” it strained the Court’s credulity to suggest that Congress truly did (or could) simply hand the issue off for unilateral decision by the attorney general:

The Government, in the end, maintains that the prescription requirement delegates to a single Executive officer the power to effect a radical shift of authority from the States to the Federal Government to define general standards of medical practice in every locality. The text and structure of the CSA show that Congress did not have this far-reaching intent to alter the federal-state balance and the congressional role in maintaining it.

Thus, Justice Kennedy and the Court struck down the attorney general’s implementation of the act; if Congress truly wanted to empower the executive branch to decide the assisted-suicide question, then Congress would have to amend the statute and clearly command that policy.

As one might now suspect, this could be the point that Kennedy was pressing in the Hobby Lobby arguments. Abortion, including methods of contraception that induce early abortion, is among the most contentious political issues of our time—far more controversial than assisted suicide was when Gonzales v. Oregon came before the Court. Kennedy knows this better than anyone: He cowrote the opinion that reaffirmed Roe v. Wade’s basic right to abortion in its moment of greatest peril, and he wrote the opinion affirming Congress’s power to prohibit partial-birth abortion. He and his colleagues are well aware of the “earnest and profound debate” surrounding the abortion issue; he’s looked down upon the plaza before the courthouse and seen the protesters. And now he and his colleagues have been asked by the government to affirm that a single cabinet secretary can unilaterally decide that religious persons must pay for other people’s contraceptives and abortifacients, or incur a tax for their refusal to pay, based on one modestly worded statute.

Perhaps Justice Kennedy’s intended audience at oral argument was not so much the lawyers, or even the agency, but Congress and the general public: If this nation is going to erect a new program for funding people’s access to abortifacients and contraceptives, a policy fraught with fundamental questions about religious liberty, then Congress must pass statutes more specific than merely providing for “minimum essential coverage.” Perhaps Justice Kennedy means to say, as he quoted in Gonzales, that “Congress could not have intended to delegate a decision of such economic and political significance to an agency in so cryptic a fashion”—all the more so when Congress also has passed a statute, the Religious Freedom Restoration Act, requiring the government to minimize burdens on religious liberty, not needlessly exacerbate them.

Whether or not this is what Justice Kennedy had in mind during the Hobby Lobby arguments—and he surely will make clear his position soon enough—we can expect the modern administrative state to raise many more questions of constitutional principle in the future. The establishment of the administrative state, in both the Progressive Era and the New Deal, raised challenging questions about constitutional structure and rights. We seem to find ourselves in a similar moment once again. The administrative state’s vigorous growth, in both scope and intensity, has returned it to the center of constitutional debate.

So far, this has been seen most clearly in matters of federalism, as law professor Gillian Metzger noted in a 2008 article. In an era when the Supreme Court was largely unwilling “to impose significant constitutional limits on the substantive scope of Congress’s regulatory powers,” the same Court took steps to ensure “that the impact of challenged agency decisions on the states is considered.” Perhaps Metzger’s diagnosis of the Court’s unwillingness to impose limits was too pessimistic, especially as seen in the Court’s willingness to overturn the Affordable Care Act’s encroachment upon state authority in the Medicaid expansion (by a 7-2 supermajority of the justices, no less). But Metzger and others are certainly on to something when they suggest that “administrative law may be becoming the home of a new federalism.”

So, too, with the separation of powers. The Court has proven its willingness to strike down altogether statutory structures that violate the separation of powers, such as the Sarbanes-Oxley accounting reform law’s attempt to create an “independent agency” within yet another “independent agency,” which the Court struck down in 2010. And perhaps the Court will do something similar in NLRB v. Noel Canning, the challenge to President Obama’s appointment of officers without Senate confirmation, now pending before the Court. But looking beyond such singular cases, the courts can also vindicate constitutional design simply in the way that they interpret statutes and review agencies’ implementation of federal statutes—statutes such as the Affordable Care Act.

“What kind of constitutional structure do we have if the Congress can give an agency the power to grant or not grant a religious exemption based on what the agency determined?” Justice Kennedy asked the question; it falls now to him and his colleagues to answer it.

Adam J. White is a lawyer in Washington, D.C.