Banning smoking in most workplaces, as Maryland did in 1995, was a major public health advance. So were the decisions by several counties and, in 2008, the state, to extend the ban to bars and restaurants. The ban on smoking in Howard County's parks, which County Executive Ken Ulman plans to announce tomorrow, not so much. Bartenders and waiters faced a real risk of health problems from secondhand smoke as a result of their work conditions, but a family going for a picnic in Centennial Park faces little or no danger from someone taking a puff 100 yards away. Even Dr. Peter Beilenson, the county's health officer, admits that the direct public health benefit of this move is modest.

Nonetheless, it is a good idea, and other jurisdictions and the state should follow Howard's lead, for two reasons.

The first is that while second-hand smoke is not a huge risk in a park, there is a broader public health principle at work. Smokers may complain that rules like the one Mr. Ulman is enacting create a stigma around smoking. If so, good. Relatively few people in Howard County smoke — about 9 or 10 percent of the population — but that is 9 or 10 percent too many. Smoking is the single biggest preventable cause of disease and death, and the county has rightly determined that it should not be in the business of condoning it, even tacitly. Park rules are an expression of the county's values, and banning smoking in them is consistent with Howard's policy that the habit is not one it wants to encourage, or even enable.

The second reason is that smoking impedes non-smokers' right to the peaceful enjoyment of the public parks. Smokers may try to couch the rules as an impingement on their freedom, but they have the issue exactly backwards. Each individual's rights extend only until the point at which they impede someone else's rights. The presence of smoke in the air presents an annoyance to non-smokers, and it is reasonable to ban it in parks just the same as we prohibit loud music and rowdy behavior. It is certainly much more possible for non-smokers to avoid smokers in an open, expansive park than it is in a bar or office, but to expect them to do so presupposes that they should not be able to freely enjoy a park in the same way that a smoker can.

Tobacco is a legal product, and if adults want to be so stupid as to use it, they are free to do so. Howard's planned ban, doesn't change that, nor is it an example of nanny statism. The county is not telling people what to do or saying it knows best how they should live their lives. It is simply saying that it will not be a party to smokers' bad decisions, and that it will stand up for the rights of the 90 percent of its residents who don't smoke. It may not be a life-saver on the order of the existing bans on smoking in public places, but it's still worthwhile.