SEATTLE—Dale Chihuly is perhaps the world's most successful glass artist. His clients include Bill Gates and Bill Clinton, and his elaborate installations of sea gardens and flower clusters show that mere sand transformed by fire can elevate a casino ceiling to the level of gallery spectacle.

But now Mr. Chihuly is in the midst of a fight in federal court here over the distinctiveness of his creations and, more fundamentally, who owns artistic expression in the glass art world.

Mr. Chihuly has sued two glass blowers, including a longtime collaborator, for copyright infringement, accusing them of imitating his signature lopsided creations, and other designs inspired by the sea.

"About 99 percent of the ocean would be wide open," Mr. Chihuly said in an interview. "Look, all I'm trying to do is to prevent somebody from copying me directly."

The glass blowers say that Mr. Chihuly is trying to control entire forms, shapes and colors and that his brand does not extend to ancient and evolving techniques derived from natural.

"Just because he was inspired by the sea does not mean that no one else can use the sea to make glass art," said Bryan Rubino, the former acolyte named in the suit who worked for Mr. Chihuly as a contractor or employee for 14 years. "If anything, Mother Nature should be suing Dale Chihuly."

The two glass blowers say that Mr. Chihuly has very little to do with much of the art, and that he sometimes buys objects and puts the Chihuly name on them, a contention that Mr. Chihuly strongly denies.

He acknowledges that he has not blown glass for 27 years, because of injuries suffered in two accidents. Still, Mr. Chihuly said, he works with sketches, faxes and through exhortation. Nothing with his name on it ever came from anyone but himself, he said.

Andrew Page, editor of Glass: The Urban Glass Art Quarterly, which is published in New York, said that Mr. Chihuly deserved a high place in the pantheon of glass artists, but that the suit could hurt his reputation by igniting countercharges and opening a window into how a celebrity artist works on a mass scale.

"I think Dale Chihuly is a pure original," Mr. Page said. "He has a tremendous sense of color and composition. And he has done a tremendous amount for the field. But this lawsuit may have been the worst thing he could have done."

Mr. Chihuly, 64, operates out of a cavernous boathouse on Lake Union. He has 93 employees, part of a veritable fine art factory called Chihuly Inc. When celebrities like Robin Williams or Colin L. Powell visit Seattle, the boathouse is often the sole stop they want to make.

"This lawsuit is not about money," Mr. Chihuly said. "It's about what is fair. There are a million forms you can make that don't look like mine."

In a 2003 copyright case involving glass art, the United States Court of Appeals for the Ninth Circuit, in San Francisco, ruled against an artist who said another artist had used his design of jellyfish encased in glass. The two designs looked similar, but the court said no one could copyright nature.

"These ideas, first expressed by nature, are the common heritage of humankind, and no artist may use copyright laws to prevent others from depicting them," the court said. But the judges added that any artist might "protect the original expression he or she contributes to these ideas."

One question unanswered by the suit is why Mr. Rubino and Mr. Chihuly would turn on each other so bitterly. By all accounts, they worked closely for nearly 20 years on Mr. Chihuly's biggest projects, a relationship not unlike partnerships through the ages between masters and the craftsmen who carry out their work.

In court filings, lawyers for the glass artists wrote that Mr. Chihuly would "often ask Mr. Rubino to come up with something for Dale Chihuly to review and purchase for Chihuly Inc."
"Chihuly is not the source of inspiration for a substantial number of glass artwork carrying the Chihuly mark," they wrote.

In an interview, Mr. Rubino said he did not understand why Mr. Chihuly went after him and said the suit could ruin him. He said it could prevent him from making the most basic of glass objects that are lopsided by gravity when pulled from an oven.

For his part, Mr. Chihuly called Mr. Rubino a glassblower who labors around a furnace at the instruction of an artist. Asked to assess Mr. Rubino, Mr. Chihuly said, "He was an excellent craftsman" with little vision of his own. "You think I would ever let Rubino decide what something looks like?" Mr. Chihuly asked.
Mr. Rubino's lawyer, Scott Wakefield, said Mr. Chihuly was in essence seeking a monopoly over a huge field of art.

"If the first guy who painted Madonna and Child had tried to copyright it," Mr. Wakefield said, "half of the Louvre would be empty."