On Wednesday, the Supreme Court confronted the latest frontier in the battle over strip searches: Does the Constitution allow prison officials to conduct a strip search of everyone arrested for a minor offense, no matter how trivial? And instead of focusing on high principles, the arguments took a surprisingly graphic turn. The lawyer for the largest county jail in New Jersey insisted that prison officials could have conducted a “true anal cavity” search of someone arrested for speeding, but instead resorted simply to an “anal focus and genital focus” search, requiring him “to lift his genitals and to squat and cough,” so that any drugs concealed in his body cavities would fall out. “You want us to write an opinion that applies only to squatting and coughing?” asked Justice Scalia, as the courtroom broke into nervous laughter.

But if the mechanics of strip searches were embarrassing to the justices as well as the arrestees, the constitutional stakes could hardly be higher. For decades, federal courts had held that people arrested for minor offenses couldn’t be strip searched unless prison officials had reason to suspect them of concealing weapons or contraband. But over the past three years, some federal appellate courts have reached the opposite conclusion. By reaffirming the traditional prohibition on suspicionless strip searches, the Supreme Court can resurrect a basic constitutional principle that it has allowed to erode in recent years: namely, that the intrusiveness of a search should be proportional to the seriousness of the suspected crime.

The facts of the latest case, Florence v. Board of Chosen Freeholders of Burlington County, could hardly be more sympathetic for defenders of privacy. Albert Florence was stopped by a New Jersey state trooper while riding with his wife and daughter in their BMW sport utility vehicle. Florence, who is African American, has been stopped for speeding when driving in fancy cars before (he works for an auto dealership), and he believes he was the victim of racial profiling. Florence’s wife, who was driving, insisted they weren’t speeding, but the trooper checked his records and found an outstanding warrant for Florence’s arrest, issued on the premise that he hadn’t paid a fine for a previous traffic offense. Florence showed the trooper a document indicating that he had, in fact, paid the fine, but the trooper handcuffed him and took him to the Burlington County jail. He remained in prison for 6 days, despite a New Jersey law requiring him to be taken before a judge after 72 hours, and was strip searched twice. Finally, Mrs. Florence obtained another document proving that her husband had paid the fine and a judge, declaring himself “appalled” by the incarceration, ordered his release.

During the oral arguments on Wednesday, the justices debated what the framers of the Fourth Amendment would have thought about strip searches. (Justice Scalia was especially interested in the fact that prisoners in the colonial era would strip each other naked in a ritual cleansing process of ablution.) But this historical trivia missed the more important point: At the time of the Framing, juries had the discretion to rule against the government in cases where the intrusiveness of a search outweighed the seriousness of a crime. In the case that inspired the Fourth Amendment’s prohibition on unreasonable searches, for example, a British jury awarded John Wilkes a thousand pounds after the King’s agents searched his desk drawers for evidence that identified him as the author of an anonymous pamphlet criticizing the King. In the jury’s view, the crime of which Wilkes was suspected—seditious libel—didn’t justify such an intrusive search of his most intimate papers and effects.

During the early twentieth century, this proportionality principle was retained in criminal statutes: During Prohibition, for example, it was illegal to sell alcohol, but not to purchase or possess it. That sensible limitation was abandoned, however, during the war on drugs, when Congress and the states imposed ruinous penalties on drug possession and purchase. This effectively spelled the end of the proportionality principle: Suddenly the police could approach anyone whom they suspected of carrying a small amount of drugs and do a full body pat down or car search. The principle eroded further as the police began to use low-level traffic violations as a pretext for enforcing the drug laws: They could pull over virtually any motorist for speeding or turning without signaling, and use the encounter as a pretext to look for drugs. As Albert Florence learned, giving the police a blank check to stop anyone they viewed as suspicious led to an explosion of racial profiling. At the same time, states increasingly authorized arrests for low-level traffic violations: In Washington, D.C., for example, you can be arrested for driving with an expired license plate. If the Supreme Court upholds strip search for any arrest, no matter how minor, then drivers with expired plates could be not only hauled off to jail but strip searched as well. And strip searches for traffic offenses would be pointless, as well as unfair: Justice Stephen Breyer found only one case out of 64,000 where someone arrested for a low-level crime smuggled drugs into jail that might have been discovered in a strip search.

If, by contrast, the Court uses the Florence case to reaffirm the rule that people arrested for minor offenses can’t be strip searched without some reason to suspect them of concealing weapons or drugs, the decision could have broader and more beneficial consequences. Citizens could invoke the decision to insist that the Fourth Amendment contains a proportionality principle—requiring courts to balance the intrusion on the individual against the intensity of the state’s interest in investigating or prosecuting a particular crime. Armed with this proportionality principle, courts might allow for intrusive forms of virtual surveillance—such as GPS tracking, which the Court will debate in November—when the police are investigating serious crimes, such as murder or large-scale drug operations, but not low-level crimes, such as traffic violations. That’s precisely the kind of balancing that juries used to perform at the time of the Framing. Rather than representing a departure from the original understanding of the Fourth Amendment, therefore, a decision forbidding routine strip searches for suspected traffic offenders would return to its bedrock principles.

Jeffrey Rosen is legal affairs editor of The New Republic.