Few art historical issues are as contentious, or have as dramatic and immediate effects in the marketplace, as those of attribution and authentication. In fact, lawsuits are so common that many experts require owners to sign a statement promising not to sue before they will even look at a work and offer an opinion. Among those who require such a signed statement is the Andy Warhol Art Authentication Committee, which was set up in 1995 by the Andy Warhol Foundation for the Visual Arts.

Still, that didn't stop Joe Simon-Whelan, a filmmaker who owns a painting that was rejected by the board, from suing the committee, the foundation, Warhol's estate, and the estate's sales agent in the United States District Court Southern District of New York in July. Last month, a decision by the Jean-Michel Basquiat authentication committee triggered another suit, though not against the committee itself. The dealer Tony Shafrazi and his client Guido Orsi sued Christie's, charging the auction house with fraud and false advertising for having in 1990 sold Mr. Shafrazi a painting attributed to Basquiat.

Last year, the painting, now owned by Mr. Orsi, was rejected by the authentication committee.Warhol and Basquiat are among a group of 20th-century artists whose work has recently appreciated dramatically. And one of the peculiarities of authenticating recent works seized on by numerous plaintiffs is that the "experts" are often people with a substantial interest in the valuation of the artist's oeuvre, like the artist's primary dealer, his heirs, or a foundation set up to extend his legacy.

In France, the principle of droit moral gives an artist and his heirs, for 70 years substantial control over his name and his works, including the right to challenge the authenticity of a work purporting to be his. But in America, no one, technically not even the artist himself, has a legal right to decide whether a work is authentic or not. Instead, the power of an expert or an appointed board of experts follows only from their general credibility and knowledge of the artist's oeuvre. Mr. Simon-Whelan, in his suit, describes what he alleges is a "20-year scheme of fraud, collusion, and manipulation" to control the market in Warhol's artwork.

He argues that the committee maintains a monopoly on the authentication of Warhol works and fraudulently rejects genuine works in order to limit the supply and thereby increase the value of works owned by the foundation. Mr. Simon-Whelan's work, an untitled self-portrait allegedly by Warhol, was, according to his suit, authenticated in the late 1980's before the authentication board was set up by both the sales agent for the estate, Vincent Fremont, and the then executor of the estate, Fred Hughes. In 2001, while offering the painting for sale for $2 million, Mr. Simon-Whelan submitted it to the board for authentication. They rejected it, twice first in 2002, and then, after he re-submitted it with more documentary evidence, in 2003.

The relationship between the Warhol Foundation and the authentication board is complex. A recent article in the New York Times quoted the Warhol Foundation's chief financial officer, K. C. Maurer, as stating that the foundation is wholly separate from the authentication board, but that is not true. One of the board's five members, Sally King-Nero, is also an employee of the foundation. Ms. King-Nero and another board member, Neil Printz, are also co-editors of the catalogue raisonnée of Warhol's paintings and sculptures, which is being sponsored by the foundation.

The editing of the catalogue raisonnée in essence constitutes a separate, parallel process of authentication. similar structures and authentication processes are in place for other 20th-century artists. The Pollock-Krasner Foundation is, like the Warhol Foundation, a grant-giving institution. From around 1990 until 1996, there was also a Pollock-Krasner Authentication Board, set up by the foundation and responsible for authenticating works by Jackson Pollock and his wife, Lee Krasner. The Alexander Calder Foundation, run by Calder's grandson, Alexander Rower, also authenticates works for the purpose of inclusion in the catalogue raisonnée. The works are examined by Mr. Rower and a group of five or six others.

There is potential for conflict of interest in all of these situations — although Mr. Rower said in an interview that "no one would ever suggest there was a conflict" if a board made everyone happy, by ruling that every object submitted was real. Among the striking aspects of Mr. Simon-Whelan's suit is his assertion that the authentication board represents a "monopoly," in violation of New York State's antitrust law. He is not the first to try such an argument. Last March, a collector from Singapore sued the estate and the daughters of the Indian artist Francis Newton Souza in New York State Supreme Court, for interfering in the collector's attempt to sell several paintings he claims are by Souza at Christie's, Sotheby's, and Bonham's. (One of the daughters contacted each auction house to say she did not believe the paintings were by Souza, and the auction houses withdrew them.)

The suit charges the defendants with libel, product disparagement, and unfair competition, among other things, and argues that they are trying to destroy competition in order to increase the value of their own collection of Souza paintings. In the mid-1990's, two plaintiffs brought antitrust claims against the Pollock-Krasner Foundation and the Pollock-Krasner Authentication Board. Both lost. The first case was dismissed on statute of limitations grounds. In the second, the judge didn't accept that the board was a monopoly. One basic problem with antitrust claims against an authentication board is this: In what, exactly, does the board have a monopoly? Not in the sale of the artist's work, since it doesn't sell work.