Lately, I've been thinking about "nanny state" issues. Sometimes governments require citizens to do common-sense things, but at what point do such laws represent intrusions on personal liberty?

A classic case in point just came up in South Dakota. Governor Mike Rounds vetoed a bill that would have required children up to age 8 who weigh less than 80 pounds to ride in booster seats in cars.

The Argus Leader reports that Rounds felt compliance would be difficult in too many cases, such as when friends and neighbors are driving kids to the movies. Would they have to weigh them before letting them into the minivan?

"I do not believe mandating and criminalizing their conduct is good public policy," Rounds wrote in his veto message. "Sometimes, good advice does not make good law."

Rounds has a point. He said the law would be unenforceable. But laws such as these often serve more as advice than as something that's enforced, signaling citizens about basic safety precautions. The bill's sponsor said his action was prompted after he told a woman that a booster seat would be safer for her kid. She told him, "If it's that important, the government would make me do it."

"I realized that people do look to government for leadership on safety issues," he said.

This is a classic reaction from a legislator. Some bad thing has happened, so there ought to be a law to address it. Which brings us back to the original question. When is it government's business to offer us advice or enforce such advice, and when should people be left alone to make their own decisions in life?

A law like this sounds to me like it will do more good than harm, but do governments always know best?