The Los Angeles Times points to the many political calculations behind the recently proposed artist re-sale royalty bill which attempts to throw the auction houses under the bus by exempting dealers, collectors and a myriad of other entities from the bill:

The bill exempts private sellers, art dealers and galleries from having to pay a royalty. Bruce Lehman, who played a key role in drafting it as counsel for the Visual Artists Rights Coalition, a group of artists and two major American organizations that represent artists in copyright matters, said that focusing only on the big auction houses will capture most of the resale market while simplifying enforcement and avoiding what would otherwise be a likely outcry from the far more numerous ranks of art dealers. [emphasis added]

Sales handled by dealers aren’t done openly like public auctions, and monitoring dealer sales would be difficult and probably expensive, said Robert Panzer, executive director of VAGA, which along with the Artists Rights Society is one of the two main New York-based organizations that represent member artists in copyright matters.

The bill specifies that “collecting societies” such as VAGA and the Artists Rights Society can keep up to 18% of the royalties paid to cover the cost of collecting and distributing the money to their members. Lehman said the 18% comes from what musical performing rights societies such as ASCAP and BMI, which represent songwriters and composers, typically incur while administering their members’ copyrights.

Nationwide Royalty on Artwork Sales Introduced in Congress (Los Angeles Times)