A ruling yesterday by the United States Supreme Court will cast a shadow over one of the successes Governor Spitzer claimed during his tenure as attorney general: his work to curtail online purchases of cigarettes.

Online cigarette sales, Mr. Spitzer and other state attorneys general found, were allowing smokers to evade taxes and permit minors to get around age requirements. Some states, such as New York, enacted criminal penalties for truck drivers who knowingly delivered boxes of tobacco. Mr. Spitzer used an investigation to leverage the United Parcel Service into giving up the transporting of tobacco to smokers nationwide.

Yesterday the federal high court unanimously struck down a Maine law that forbids deliveries of tobacco to individual consumers and burdens truckers with enforcing the law. The law is similar, though not identical, to New York’s.

“The Supreme Court’s ruling has a breadth that suggests states will have to revisit laws that are akin to this,” the lawyer who successfully challenged the law on behalf of several trucking associations, Beth Brinkmann of the firm Morrison Foerster, said in an interview.

A spokesman for Attorney General Cuomo, Mr. Spitzer’s successor, said the office was reviewing the Supreme Court decision.

So far, New York’s law has survived court challenge. A federal appeals court in Manhattan in 2003 upheld the law against claims that it violated the Constitution’s commerce clause by favoring instate tobacco retailers. But the challenge to the Maine law the Supreme Court heard was brought under an entirely different legal theory.

Trucking associations in New Hampshire, Vermont, and Massachusetts said the Maine law was pre-empted by a federal law that forbids a state from enacting a law “related to a price, route, or service of any motor carrier.”

The Supreme Court’s main concern was that Maine’s law, coupled with other laws, undermined Congress’s effort to deregulate the trucking industry. “To interpret the federal law to permit these, and similar, state requirements could easily lead to a patchwork of state service-determining laws, rules, and regulations,” Justice Breyer wrote for the court. “That state regulatory patchwork is inconsistent with Congress’ major legislative effort to leave such decisions, where federally unregulated, to the competitive marketplace.”

The trucking industry has criticized the state laws as being not only burdensome but also, ultimately, ineffective. Online cigarette retailers, industry representatives say, sidestep the laws by shipping through the federal United States Postal Service, which is not subject to state laws.

“Why should the mailman be able to deliver them to your door and the UPS driver has to go to jail?” the president of the New York State Motor Truck Association, William Joyce, said.

In 2004. Mr. Spitzer’s office opened an investigation into whether UPS had violated New York State law by shipping cigarettes to individual smokers. In return for the shuttering of the investigation, UPS signed an agreement with Mr. Spitzer that announced the company had made “a business decision” to stop shipping cigarettes to individual smokers anywhere in the country.

Under the agreement, UPS can back out if New York’s law is declared invalid or enjoined by a court.

UPS is not likely to use the Supreme Court ruling as a hook to try to get out of that agreement with New York.

“We have a policy that’s been in effect for almost three years now and has been effective, and we see no reason to change it,” a UPS spokesman, Norman Black, said.