The comic-book-inspired Sin City is No. 1 at the box office right now. Last year, its director Robert Rodriguez quit the Directors Guild of America in a dispute over whether he could bring on the author of the comic, Frank Miller, as a credited co-director. A reader asks: What happens to a director who’s not in the guild?

For one thing, he can’t direct for the biggest studios. Rodriguez was forced to drop out of Paramount’s mega-budget John Carter of Marsproject last May. Paramount is a signatory to the DGA’s basic agreement, which means that all directors, assistant directors, and unit production managers it hires must be guild members. But Rodriguez has enough name recognition that he should be able to find work easily. He can still make movies with smaller production companies, such as his own Troublemaker Studios in Austin.

Why couldn’t Rodriguez bring in a co-director? The guild has stuck to a one-director-per-film policy since 1978, to keep producers and stars from demanding “gift credits.” Exceptions are made under special circumstances: The guild recognizes “bona fide directing teams,” like the Coen brothers, the Farrelly brothers, and the Wachowski brothers; and the policy can be waived for directors on films with multiple languages or stories. Rodriguez was unable to get a waiver for Frank Miller, who had never directed a movie before, so he quit the guild.

Production on Sin City went ahead anyway, because the production companies—Troublemaker and Dimension Films—are not guild signatories. They were only observing guild rules at first because Rodriguez himself was a member, and if you hire one guild member, you’re obligated to follow guild procedure. Many indie studios decide whether to use a DGA crew on a case-by-case basis. When they want to, they can create a “single-purpose corporation” to make a film; this temporary entity can then sign on with the guild on its own, while the studio keeps its options open for future projects.

Using DGA members can cost a lot of money because the basic agreement specifies minimum salaries for each guild member on the crew. A director, for example, is guaranteed between $8,000 and $15,000 per week, depending on the size of the production. The guild also ensures that its members receive fees (called “residuals”) when the film is released on video, DVD, and television. On the other hand, many of the best assistant directors are guild members, and skilled personnel can often save money for a studio by making sure the work gets done on schedule.

Rodriguez has quit the guild once before, so he could direct a portion of the multipart, non-guild movie Four Rooms—which was co-directed by Quentin Tarantino and two others. In 1996, Tarantino lost out on the chance to direct an episode of The X-Files because he wasn’t a guild member. George Lucas is a famous guild-quitter. He split with the organization over a credit sequence in The Empire Strikes Back *.

Next question? Explainer thanks Morgan Rumpf of the Directors Guild of America.

Correction, April 13, 2005: The original version of this column stated that George Lucas quit the DGA over the credit sequence in Star Wars. In fact, the dispute was over the credit sequence for The Empire Strikes Back.