With the Supreme Court scheduled to hear oral argument next week in marriage equality cases, everyone is looking to the marriage cases the Court decided in 2013 in an attempt to predict what it’s likely to do this time around. But another recent case on a very different topic may actually have much more to say about marriage equality than one would think: last year’s case about warrantless searches of an arrestee’s cell phone. In that case, the Court held such searches unconstitutional and underscored a principle that bears on the marriage discussion—namely, that constitutional protections cannot be undone by popular vote.

The basic question in the marriage equality cases is simple. Does the Fourteenth Amendment—which prohibits states from denying any person “liberty... without due process of law” and “the equal protection of the laws”—bar state bans on same-sex marriage? The text and history of the U.S. Constitution, not to mention the Court’s own precedents, make clear that it does. Opponents of marriage equality thus are resorting to what is becoming a familiar argument, saying marriage equality should be decided not by the courts, but by the people. By that logic, citizens of individual states can trump the Constitution’s broad equality guarantee if they vote to do so.

One of the most significant statements of this view can be found in the lower court opinion the Court is reviewing. Last year, federal appeals court judge Jeffrey Sutton described the question in the marriage equality cases as a “debate about whether to allow the democratic processes begun in the States to continue... or to end them now by requiring all states in the Circuit to extend the definition of marriage to encompass gay couples.” He noted that “[i]n just eleven years, 19 states and a conspicuous District, accounting for nearly 45 percent of the population, have exercised their sovereign powers to expand [the] definition of marriage.” He described that “timeline” as “difficult... to criticize as unworthy of further debate and voting.” Unsurprisingly, defenders of that opinion have continued this line of argument in the Supreme Court.  One of the parties’ briefs argues that the Court should adopt a deferential standard in reviewing state marriage bans because that standard “defers to voters in order to protect the democratic process.” Another asserts that “[t]he Constitution delegates most sensitive policy choices to democratic debates, not judicial mandates.”

These arguments about “democratic process” may seem more attractive than some of the other arguments made by opponents of marriage equality. For instance, leaders of the 2012 Republican National Convention Committee on the Platform filed a brief arguing that marriage bans are constitutional because, in part, men need “traditional marriage” so women can “‘transform [their] male lust into love.’”

But there’s a basic flaw in the “democratic process” arguments, as last year’s cell phone search decision confirms. They get the Constitution exactly backwards.

In Riley v. California, the Court considered whether the police may without a warrant search someone’s cell phone following an arrest. The Court held, in a unanimous opinion, that the answer is no; such searches are generally prohibited by the Fourth Amendment’s requirement that “[t]he right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures... not be violated.” Recognizing that “unrestrained search[es] for evidence of criminal activity” was “one of the driving forces behind the [American] Revolution,” the Court concluded that warrantless cell phone searches permitted too great an intrusion on privacy and thus should not be allowed, absent exigent circumstances preventing the police from obtaining a warrant. As Chief Justice Roberts explained in the Court’s opinion, modern cell phones are “now such a pervasive and insistent part of daily life that the proverbial visitor from Mars might conclude they were an important feature of human anatomy,” and they can contain a vast amount of “sensitive personal information.”

Justice Alito agreed with the rest of the Court that such searches were unconstitutional, but he wrote separately to make two points, one of which has bearing on the marriage equality cases. Alito wrote that he “would reconsider the question presented here if either Congress or state legislatures, after assessing the legitimate needs of law enforcement and the privacy interests of cell phone owners, enact legislation that draws reasonable distinctions based on categories of information or perhaps other variables.” Put differently, Alito would allow Congress and state legislatures to change the Court’s answer in Riley. Even though the Court had concluded that the Fourth Amendment’s prohibition on “unreasonable searches and seizures” generally prevents the police from engaging in such searches, Alito would allow Congress and state legislatures to decide that “the legitimate needs of law enforcement” outweigh the “privacy interests of cell phone owners.”

Tellingly, no other Justice joined Alito’s opinion. Not one. And that tells us a great deal about the “democratic processes” position adopted by Judge Sutton and advanced by opponents of marriage equality. What the rest of the Court implicitly recognized in Riley was that Alito’s approach is fundamentally wrong. Congress and state legislatures may be able to supplement the Constitution’s protections—indeed, they may sometimes be well-suited to doing so, as Alito noted in a different Fourth Amendment case about GPS monitoring—but they cannot scrap them.

Indeed, that is a point so fundamental to our constitutional order that the Supreme Court has made it repeatedly in various contexts, noting that fundamental constitutional protections “depend on the outcome of no elections,” and “[a] citizen’s constitutional rights can hardly be infringed simply because a majority of the people choose that it be.”  As recently as 2011, in a campaign finance case, Roberts explained that “the whole point of the First Amendment is to protect speakers against unjustified government restrictions on speech, even when those restrictions reflect the will of the majority.” The Constitution, not voters, has the ultimate legal authority. In the past, the Court hasn’t treated the Fourteenth Amendment any differently than the First and the Fourth. In 1996, for example, it struck down a state constitutional amendment adopted by state voters because it violated the Fourteenth Amendment.

When the Court considered the scope of the Fourth Amendment’s protections in Riley, it didn’t say it was up to Congress or state legislatures to decide how much privacy Americans enjoy when it comes to their cell phones. Instead, the Court considered the text and history of the Fourth Amendment, as well as the Court’s precedents. The Court should do the same thing this year when it considers the scope of the Fourteenth Amendment’s protections in the marriage equality cases. If it does, there’s no question what the result should be: a resounding victory for marriage equality.