Technology has allowed cars to be safer—anti-lock brakes to prevent lock-up and skidding, air bags to provide protection in a crash and Bluetooth to allow hands-free phone calls are just a few examples. The first two are pretty much standard equipment nowadays, and the latter is becoming more widespread.

But some automobile manufacturers are considering adding another option in the name of safety: an ignition interlock, or alcohol sensor, to prevent someone from driving while drunk.

On the surface, this seems like a reasonable enough idea. After all, no one is in favor of drunken driving, which resulted in nearly 13,000 traffic deaths in 2007 (a favorable 38% decrease since 1982). But should such devices be ubiquitous and should everyone—regardless of their driving history—be forced to pass an alcohol test to be able to drive their car?

Some safety advocates, such as the Governors Highway Safety Association, Mothers Against Drunk Driving and several states (New Mexico, New York, Pennsylvania and Oklahoma) seem to think more universal application would be a good idea.

Certainly, ignition interlock devices make sense for the most dangerous drunken drivers—those with high blood-alcohol content (the legal limit is 0.08 BAC, and the average BAC for a drunken driver involved in a fatal crash is more than twice that), who also happen to most likely be repeat offenders. But requiring the rest of the driving public to pass the same test makes us a society of suspects and violates the fundamental principle of presumed innocence.

Furthermore and more troubling, once this technology—which has advanced to include passive mechanisms like steering wheel sensors, retinal scans and alcohol sniffers—comes as standard equipment in all cars, it will be set well below the legal limit of 0.08.

Twenty-four states have what is known as “presumptive intoxication levels,” which means that a driver can be arrested and convicted of DUI at levels as low as 0.04 and 0.05 BAC. In all states, mandatory interlocks would be set below those levels, due to product liability concerns and variances in technology. Interlocks in all cars set at such low levels would effectively eliminate the ability to drive after having only one drink for many adults.

Imagine if you were home having a glass of wine with dinner and you get a call that one of your children is hurt or sick and in an emergency situation. Imagine not being able to get to them because your car decided that the wine you just drank was enough to lock you out of driving. That’s not an anti-drunken driving safety device; that’s a neo-Prohibitionist enforcement device—evidence that groups such as MADD have strayed from their original purpose to combat drunken driving.

There is also a practical aspect to making ignition interlock mandatory on all cars. Let’s assume that ignition interlock technology is nearly perfect—99.99% accurate (which is generous and highly unlikely) in correctly measuring BAC. If half of all the licensed drivers (120 million people) drive to and from work each day, the number of false positives—i.e., people incorrectly identified as exceeding the set BAC limit—would be 12,000 each time those people tried to start their cars. So 24,000 times a day, drivers who simply are trying to drive to work or pick up their children from school each day would be prevented from driving their cars because they were erroneously identified as drunk.

If not everyone, then why not mandate ignition interlocks for everyone convicted of drunken driving? Because an important principle of jurisprudence is that the punishment should fit the crime. Someone exceeding the speed limit by 25 mph (usually considered reckless driving) receives a different punishment than someone who is only 5 mph over the posted speed limit.

So someone—especially a first-time offender—at the legal limit of 0.08 BAC should not automatically receive the same punishment as someone driving at more than twice that and with prior convictions. For the former (and it’s worth noting for perspective that various studies indicate driving while talking on a cell phone is more dangerous than driving at 0.08 BAC), the court should have the discretion to determine the appropriate punishment. This would not preclude an ignition interlock if circumstances warranted.

One of many of Mark Twain’s memorable phrases is: “To a man with a hammer, everything looks like a nail.” Ultimately, that is the problem with the ignition interlock proponents. It can be an effective device to use with high BAC and habitual drunken drivers. But it’s a solution in search of a problem for the rest of society.