Listen, I'm a small-government conservative. When New York banned all smoking in public places, I protested. When they came for foie gras in Chicago, I ridiculed. But when Mayor Bloomberg proposed banning trans fats in New York City restaurants, I murmured: "Gee, is that really so bad?"

Denmark has banned trans fats. New Jersey and the District of Columbia are thinking of following New York City's lead.

It's easy to drop any new idea into an old formula: "Nanny state threatens our freedom!" "What's next? Banning butter?" And it is true: People who would be appalled at letting government regulate my consumption of, say, pornography seem to have no problem getting between me and my doughnuts. But the easy and the formulaic are not always correct.

What's the difference with trans fats? Two things. In the first place, most foods that endanger health do so not because they are bad in themselves, but because too many of us (yes, that's me) do not practice moderation. Fat isn't bad for you. Too much fat is bad for you. Too little and you die; too much leads to bulging waistlines and clogged arteries.

But by contrast, there is no level of consumption of trans fats that is good for you. Ideally, we should all consume zero.

But here's the really key second difference: Trans fats are not exactly a food. They are a byproduct of an industrial process (hydrogenation) introduced to help stabilize the shelf life of cooking oil.

Of course, it's hard to make the case for a government ban today when the reason we consume so much hydrogenated oils is that the same folks who are yelling about trans-fattiness urged places like McDonald's to switch from beef tallow to hydrogenated vegetable oil. I don't blame people for feeling aggrieved or skeptical. But the emerging science of trans fats really does appear to justify the concern: Unlike saturated fats, trans fats in sufficient quantities both raise bad cholesterol and lower good cholesterol, a double whammy to the heart. They exist primarily as a result of a man-made process.

Why should industrialists be permitted to adopt a process that gives some people heart attacks?

My libertarian impulses include the feeling that informed people who really want to undertake the risks of trans fats should be allowed to do so. In a perfect world, a small mom-and-pop restaurant would be able to pay a "vice tax" and receive a license to use trans fats, provided they prominently display that they are doing so. People who need that trans fat fix could go and get it (probably at much less cost to their health, since the normal food supply would be drained of trans fats). But what too many conservatives are now promoting is the idea that when people dine out they should be able to spot and avoid an invisible industrial process that endangers their health. That seems to me like a parody of personal responsibility.

Trans fats are only a small part of our national epidemic of heart disease, but they are an unjustifiable part.

There's an old saying, "Don't throw the baby out with the bathwater." But in this case, there is no baby there. Throw it out.