These questions have proved exceedingly difficult for courts to answer. So instead, jurists have usually punted on the question—as the Supreme Court did as recently as last month—and deferred to the judgment of the police. The consequences for our civil liberties have been serious. For example, nearly a century’s worth of punting gave rise to “driving while black,” the racial profiling of African American motorists for traffic stops. Even as Americans have built a society around cars, judges have abdicated their role of limiting law enforcement’s power over people’s daily lives.

From the automobile’s early years, Americans have viewed cars as their private spaces and as symbols of liberty. Unsurprisingly, manufacturers have capitalized on the ready symbolism. “To own a Ford car is to be free to venture into new and untried places,” a 1924 advertisement proclaimed. Almost a century later, a commercial reimagined a scene from the Revolutionary War with American soldiers charging British redcoats in Dodge Challengers. The tagline: “Here’re a couple things America got right: cars and freedom.”

But to exercise this freedom, people need permission from the government, granted in the form of a driver’s license. Ever since the mass production of cars began, states have regulated their use because too much individual freedom on the road wreaked havoc and threatened everybody else’s safety and freedom of movement. No one seriously advocates a rebellion against licensing requirements and traffic laws. Without state intervention, more lives would be lost to dangerous driving, and our highways even more clogged with traffic. Without the assurance of safety, driving to work, the grocery store, the gym, a place of worship, a friend’s home—basically any place in American society where a car is widely viewed as necessary to live fully and independently—would be perilous. For these reasons, the privilege of driving justifiably comes with many strings attached.

But how many strings is too many? The Supreme Court could have provided some clarification in its most recent term, but it didn’t. In Mitchell v. Wisconsin, the police found the defendant near his car and very drunk. Because he passed out before he could perform a breath test, the officer ordered a blood test without first obtaining a warrant. Wisconsin authorizes this warrantless action if a motorist is unconscious.

While more than half the states have similar laws on their books, every single state has a less intrusive version, which requires motorists suspected of drunk driving to perform a breath test. These laws are called “implied consent” laws, a term that reflects the fact that cooperation is necessary for either a breath or blood test. Subjects must breathe deeply and exhale for a minimum length of time, sometimes repeatedly, into a mouthpiece. They must sit still while blood is drawn. Anticipating that most drivers wouldn’t willingly participate in evidence-gathering against them, state laws have made consent to these tests a condition of driving. In other words, by receiving a license to drive, the motorist has, implicitly, given consent.