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.