Bowing to common sense, the Rhode Island Supreme Court threw out a ruling against three firms that sold lead paint long ago. The unanimous decision derails, at least in this state, a case whose flammable mixture of big business, children and emotion could have set a dangerous precedent — in part because the state sought to punish people for doing things that were not illegal at the time they were done. That’s grotesque injustice, however alluring to some politicians seeking votes.

First filed in 1999, the case accused four paint companies of selling lead paint after it was banned in 1978 as dangerous to children. After a mistrial in 2002, another Rhode Island jury found three of the four liable in 2006. The companies asserted that they had sold no lead paint here after the ban, that they had stopped producing lead-based pigment decades before that, and that no single house in Rhode Island was shown to have been painted with their lead paint. But the jury disagreed. The firms were ordered to spend $2.4 billion to abate the lead in up to 240,000 houses (about $15,000 a house) built in the Ocean State before 1980.

The companies’ victory on appeal should slow or stall a growing legal movement that holds manufacturers liable based on public-nuisance law rather than the product-liability law typically used in cases against manufacturers. Liability in public-nuisance cases rides on judgments as to the injury to consumers rather than the conduct of defendants. Plaintiffs’ trial lawyers try to use the greater ambiguity of nuisance law to cash in on settlements without having to prove specific instances of bad conduct.

Public-nuisance theory was used to bring lawsuits against the tobacco industry in 46 states, but they settled out of court and the theory was never tested before a judge.

The adverse ruling ends the vision of sugar-plums dancing in the heads of lead-abatement contractors (and in the nightmares of responsible landlords and homeowners).

Laws at the state and local level already bar lead paint in houses. It is encouraging that blood levels in Rhode Island children have been dropping dramatically for years. It has always been, and should remain, the responsibility of property owners (and parents) to assure the safety of children. If such laws are ignored, it is those who ignore them who are to blame for the result, not the companies that stopped making and selling the paint years ago.

Lead paint is dangerous, but so are lots of petroleum-based products when misused, as are many other products. Rhode Island’s lead-paint case, if affirmed, could have opened the door to lawsuits against, say, liquor distributors and auto makers for their customers’ irresponsible mixture of drinking and driving. Fat people might sue fast-food chains. Crime victims might decide to sue gun makers with deeper pockets than the robbers who shot them. A producer of comfortable pillows might be sued by a jobseeker who slept through a job interview. Absurd? We’re already headed in that direction.

An economy in which almost every manufacturer is held hostage to the misuse of its products is an economy that will collapse. If Tuesday’s decision helps stop those crusades based on the improper interpretation of public-nuisance law, then the judges have struck a blow for rational and fair public policy.