As early as 2026, all new cars and trucks sold in America will be equipped with technology that prevents them from being operated by legally drunk drivers — regardless of whether the new owners like it.

The new rule for auto manufacturers, billed as a safety measure, will require a form of breathalyzer technology to be baked into the car’s operating system. If the person behind the wheel is drunk, the car will not operate normally.

The technology, proponents say, will be passive and always running in the background. No breathing into tubes will be required. Sensors, mounted probably in the steering wheel or column, will analyze the ambient air around the normally breathing driver and detect whether that person is above the legal blood-alcohol limit.

The new regulations were included in the $1.2 trillion infrastructure bill signed into law by President Biden in November last year. They are only five paragraphs in a 1,039-page bill, but those paragraphs will dramatically change many Americans’ relationships with their cars.

The technology could conceivably put an effective end to drunk driving. An average of 28 people die every day in alcohol-related accidents in the U.S. That number would likely drop to near zero. First-responders and courts would be freed to focus on other things, and fewer lives would be destroyed by accidents involving drunk drivers.

Yet the rules raise a host of thorny questions about civil liberties, due process, property rights, and safety. A scholar studying the intersection of constitutional issues and digital privacy at the conservative American Enterprise Institute at Washington, D.C., James Harper, said he sees “all kinds of problems” with the law as it is written. First and foremost, he said, is safety.

“What about the circumstances when it is more important to get the car started than it is to prevent someone from driving drunk?” Mr. Harper asked. “Say there’s a fire racing through the valley and there’s an evacuation order and everyone empties out of a bar and the guy who’s been in there since 9 a.m. can’t get his car started?”

The law also requires technology that will judge whether the driver is “impaired” and be able to disable the vehicle if so. The law does not specify what “impaired” means. So it will be up to whoever designs the technology, or an algorithm, to decide.

When it was passed, the advocacy group Mothers Against Drunk Driving hailed the breathalyzer portion of the provision as the most significant lifesaving legislation passed in the 41-year history of the organization.

“This new law will virtually eliminate deaths and injuries caused by drunk driving,” the group’s national president, Alex Otte, said. “This is the beginning of the end of drunk driving.”

The law doesn’t specify how or what shape the technology will take, so it will be up to the automakers to decide. A coalition of automakers organized under the umbrella of the Automotive Coalition for Traffic Safety for years have been working on the technology — dubbed Driver Alcohol Detection System for Safety, or DADSS — and feel confident that they will meet the deadline laid down by Congress.

Similar technology is already being used in some states to prevent drunk drivers from repeating their crimes, and pilot projects involving fleet vehicles and trucks are also under way.

In addition to breathalyzer technology, automakers are looking at a touch system that shines a light through a finger and is able to measure blood alcohol levels through tissue spectroscopy.

The automakers are adamant that the technology will be a closed one, meaning that it will be hard-wired into the car’s operating system and not accessible remotely by third parties such as law enforcement or insurance companies. Police, hackers, or repossession companies would not, they say, be able to remotely disable someone’s vehicle.

Regardless, the AEI’s Mr. Harper is confident that the technology will be challenged in court. That cannot happen until it is already in use and someone has been affected by it. If the challenge doesn’t involve safety issues, he said, it could easily involve property rights.

“This is kind of an all-new, tech-enabled pre-seizure of personal property,” Mr. Harper said. “It’s plainly recognized as a seizure if law enforcement pulls you over and forces you to stop your car, so courts would have to recognize that some automated system that does the same thing is allowing a vehicle to be seized.”