Under federal law, members of Congress are due for a pay raise this month. The Ethics Reform Act of 1989 gives Congress annual cost-of-living adjustments, and according to its formula, representatives and senators should receive a 1.3 percent salary increase in 2012. For rank-and-file members of Congress, that would lead to a pay raise from $174,000 to $176,300.

Yet despite the Ethics Reform Act, salaries for representatives and senators have not budged since 2009. Since then, Congress has blocked these annual cost-of-living adjustments from taking effect. Most recently, a rider to the Continuing Appropriations and Surface Transportation Extensions Act, passed in December 2010, froze congressional pay in 2012. Congress similarly froze its own pay from 1994 through 1997, in 1999, in 2007 and in 2010 and 2011.

On first glance, these congressional pay freezes might seem unobjectionable. Why should a do-nothing Congress merit a pay raise while other Americans endure layoffs and pay cuts? But from a constitutional law perspective, Congress’ decision to override the Ethics Reform Act’s automatic adjustments is disturbing: It violates both the letter and the spirit of the 27th Amendment.

First, a bit of background. In 1789, James Madison introduced a proposal for a constitutional amendment providing that “[n]o law, varying the compensation for the services of the Senators and Representatives, shall take effect, until an election of Representatives shall have intervened.” In explaining this proposed amendment, Madison cited the “seeming indecorum” of letting representatives and senators “put their hand into the public coffers.” But in addition to concerns about pay increases, the amendment’s supporters also had cause to worry about politically motivated cuts in pay. At the time, members of the British House of Commons often sought political advantage by pledging to reduce their own salaries, and these self-imposed pay cuts made it difficult for men of modest means to hold public office. In 1789, Rep. Theodore Sedgwick of Massachusetts cited this British practice and warned the first Congress that congressional pay cuts might “prevent men of shining and disinterested abilities, but of indigent circumstances, from rendering their fellow citizens those services they are well able to perform.” (Sedgwick ultimately opposed the amendment — evidently because he was worried that one Congress could still cut future Congresses’ pay.) The House and Senate approved Madison’s amendment in September 1789, and six state legislatures voted to ratify it during the next two years.

However, a constitutional amendment takes effect only after three-quarters of the states have approved it, and Madison’s compensation amendment fell short of that threshold. For nearly two centuries the amendment lay dormant, until in 1982 a University of Texas sophomore named Gregory Watson wrote a research paper that examined the amendment and recommended its ratification. Although Watson’s instructor gave him a “C” on the paper, Watson launched a letter-writing campaign that elicited a more favorable response from state legislatures. Between 1983 and 1992, legislatures in 32 states voted to ratify the amendment, and in May 1992, the amendment (No. 27) took effect.

At the time, media accounts characterized the new amendment as a bulwark against congressional salary raises. According to The New York Times, “the newly ratified constitutional amendment…prohibits [members of Congress] from voting themselves immediate pay raises.” But the text of the amendment applies to any law “varying” — increasing or decreasing — congressional pay. Had Madison wished the amendment to ban only increases in salary, he had templates available. Article I, Section 6 of the Constitution establishes that no senator or representative may cut his or her term short to take a job in the federal government if that job’s compensation “shall have been increased” while he or she served in Congress. Given Madison’s choice of the word “varying” rather than “increasing,” the amendment unambiguously works in both directions.

The 27th Amendment thus prevents Congress from cutting its own pay before an election has intervened. But when Congress blocks a cost-of-living adjustment from taking effect, it does not cut its own pay per se; it keeps its pay the same. For this reason, one might argue that legislation like the Continuing Appropriations and Surface Transporta­tion Extensions Act is consistent with the 27th Amendment’s restrictions.

Yet this argument is untenable. A law that rescinds a statutorily scheduled pay raise or pay cut is a law “varying” congressional compensation. To see why, imagine that Congress were to pass a law in October of this year reducing its pay for the following year. On Nov. 6, voters across the country will go to the polls. On that date, they might credit congressional incumbents for cutting their own pay. If Congress then rescinded the scheduled pay cut in December, its members could have benefited politically from the cut without losing their salary once re-elected. This plan would clearly violate the letter and spirit of the amendment, which prevents such laws from going into effect until an election has intervened so that the people are fully informed about Congress’ compensation when they go to the polls.

But if the goal of the 27th Amendment is to ensure that the people are fully informed about Congress’ compensation when they go to the polls, and if the amendment applies equally to pay raises and pay cuts, then the Continuing Appropriations and Surface Transportation Extensions Act violates the 27th Amend­ment in exactly the same way as the hypothetical bait-and-switch described above. A lame-duck Congress may not adjust the pay of its successors after it knows the results of the election — regardless of which way the adjustment goes.

In a 1994 lawsuit before the U.S. Court of Appeals for the D.C. Circuit, now-Speaker of the House John Boehner and 27 other members of Congress presented exactly the same argument that we are now making. According to Boehner, a law that canceled the scheduled 1994 cost-of-living adjustment was a law “varying the compensation for the services of the Senators and Representatives,” and was thereby unconstitutional because it took effect before an election had intervened. The Continuing Appropriations and Surface Transportation Extensions Act was similarly passed after the November 2010 congressional election and yet it affected congressional salaries before the 2012 election. Thus, according to the speaker of the House’s expressed view, the Continuing Appropriations and Surface Transportation Extensions Act flies in the face of the 27th Amendment. While the D.C. Circuit did not decide the merits of Boehner’s argument because he had not properly raised it in the lower court, he and his colleagues are still bound by their oaths of office to uphold the Constitution and abide by its requirements. (Although Boehner ultimately voted against the December 2010 bill freezing congressional pay, he has previously voted for legislation that, by his own analysis, violates the 27th Amendment.)

Even so, the question remains: Why should we care? Although the amount in controversy is relatively small ($2,300 times 535 members of Congress is $1.23 million), the cash-strapped federal government can use every last cent. And senators and representatives, who already earn more than 3.5 times the median household income, should hardly be the objects of our sympathy.

Our argument is not that members of Congress deserve a higher salary. It is merely that a constitutional republic must operate within the confines of its articles and amendments, even when doing so might seem inconvenient. Although there are some parts of the Constitution that are relics of past times and discarded moral systems — such as Article I, Section 2 (which counted slaves as three-fifths of a person for calculating states’ taxation and representation) and Article I, Section 9 (which guaranteed that Congress would not ban the importation of slaves before 1808) — the 27th Amendment is nothing of the sort. It reflects a transgenerational conviction, first expressed in the founding era and ultimately enacted in the 1990s, that Congress should not determine its own pay between elections. The Continuing Appropriations and Surface Transportation Extensions Act does exactly that. It is therefore unconstitutional.

Eric Fish is a Yale Law School public interest fellow. Daniel Hemel is the editor-in-chief of The Yale Law Journal.