WASHINGTON — A house that floats on the water and has no power to move on its own is a home, not a vessel, the U.S. Supreme Court ruled Tuesday.

The 7-2 decision upholds laws in California, Washington and other states that say floating homes that are attached to the shore and do not travel are governed by local laws applying to homes, not by federal admiralty law regulating ships and boats.

Homeowners are able to rely on an array of state and local laws that protect property owners, and, with this decision, the same is now true for the owners of moored casinos and restaurants.

State laws give some protection to store owners for accidents and injuries suffered by their customers or their employees. But federal admiralty law gives more generous protections to sailors and harbor workers who are injured working on vessels.

Lawyers for the Seattle Floating Homes Association and a similar association in Sausalito, Calif., praised the Supreme Court ruling.

The San Francisco law firm Munger, Tolles and Olson filed a friend of court brief on behalf of the two floating-homes associations, arguing that they should be regulated as houses and not under maritime law as vessels.

The Seattle City Council has been wrestling with what constitutes a vessel as it drafts revisions to its Shoreline Management Program.

City Councilmember Richard Conlin said the court ruling seemed to support the city’s position that just because something floated, that did not make it a vessel.

It’s legal to live on a vessel, but the city prohibited new floating homes in 1990. Since then, many houseboats and barges have moored at city marinas, and some residents have argued that they meet the legal definition of a vessel and shouldn’t be restricted.

In Tuesday’s opinion, the high court narrowed somewhat the definition of a vessel.

It is not “anything that floats,” explained Justice Stephen Breyer, but something “actually used for transportation.”

The court ruled for Fane Lozman, who had parked his two-story floating home at a marina in Riviera Beach, Fla.

City officials tried to evict him from the marina and later sued him under federal admiralty law over unpaid docking fees.

They eventually seized the structure as an abandoned vessel and had it destroyed.

In upholding this decision, a federal judge and the U.S. Court of Appeals in Atlanta said the floating home was a vessel because it was capable of moving on the water, and indeed, had been towed several times, including one trip of 200 miles.

Lozman appealed, arguing his home should have been protected under ordinary real-estate laws, not classified as a ship subject to being seized.

The Supreme Court, in Lozman v. City of Riviera Beach, agreed and said a “reasonable observer” looking at the plywood-box home would conclude it was a home, not a vessel.

It was not “designed to any practical degree for carrying people or things on water,” Breyer said. He noted the home had no rudder, no steering mechanism and no source of propulsion.

The justices sent the case back to Florida, where Lozman can seek to recover a $25,000 bond taken out before his home was seized and destroyed.

Breyer also said that a vessel, once moored, can lose its legal status as a vessel. “For example, an owner might take a structure that is otherwise a vessel (even the Queen Mary) and connect it permanently to the land for use, say, as a hotel,” he said.

In dissent were Justices Sonia Sotomayor and Anthony Kennedy. They said Breyer’s “reasonable observer” standard will likely cause confusion in the lower courts.

Seattle Times staff reporter Lynn Thompson contributed to this report.