There are few circumstances in which it's legal to copy a DVD and screen it in its entirety to an audience without paying royalties. One of them is in the classroom.

That exception and others make up a patchwork of laws and rulings on the use of media for educational purposes that some professors have attempted to navigate but many others ignore altogether. What constitutes "fair use" in classes that rely on films, television shows and assorted media clips? In some ways, it's still an open question. Copyright law and court precedent set the limits, but within those limits, colleges, scholars, studios and lawyers have struggled to define when exactly it's permissible to use artistic works in the classroom and in students' assignments.

One scholarly group, the Society for Cinema and Media Studies, seeks to clarify the boundaries with a new set of best-practices guidelines for fair use. Its creators hope that it will give professors a tool for interpreting existing law as well as provide a unified set of standards to eliminate confusion between instructors and college administrations.

"Our basic philosophy is that fair use is a muscle that has to be exercised; otherwise it will atrophy," said Jason Mittell, an assistant professor of American studies and film & media culture at Middlebury College who is on the society's public policy committee that crafted the document.

Some legal questions have yet to be put to the test, especially as students and professors gain greater access to free (but not necessarily authorized) materials online. A sampling of only a few major cases outlines the potential legal minefield confronting those seeking to define fair use for visual media, and the often unpredictable criteria used by courts to set the boundaries:

• A federal court found that a 75-second clip from a 72-minute Charlie Chaplin movie featured in a news piece after his death violated fair use -- because of the segment's length and the judgment that it comprised the "heart" of the movie.
• A biographical movie about Muhammad Ali, however, was allowed to use a 41-second boxing clip -- because it was deemed a small portion of the source film and used in an "informational" context.
• In the landmark Betamax case, the Supreme Court ruled that recording even entire shows from television was legal for home use -- because, it argued, the purpose was "time shifting" rather than "library building" and posed no threat to copyright owners' royalties.

For professors who frequently rely on film clips or other media to teach their material, however, there's still a good deal of leeway: the exceptions for "face to face" and online distance education, in addition to the fair use doctrine's general protection for nonprofit educational use. Despite the broad latitude given to instructors for those purposes, however, there are always potential gray areas.

"It is important to note that neither the educational exceptions nor the statute’s definition of fair use delineate specific permissible uses," the document states. "As a result, it is somewhat unclear exactly which uses they protect and every use is subject to individual analysis. Thus, this statement does not attempt to establish specific practices that would be protected under current copyright law. Instead, it outlines basic copyright principles regarding educational use. It also describes prevalent practices in the community of film and media educators that are believed to be fair uses or otherwise permissible without copyright holder authorization."

The guidelines were created alongside a survey of film and media scholars on fair use. "There’s a ton of confusion, and that was one of the main things that came out of this survey," Mittell said. The cinema society found that 88 percent of those who responded screen works in their entirety, but only 50 percent of those in the United States said their institutions were supportive of their screening practices. Instead, they "do it undercover," he said. Five percent of respondents said they secure formal permission rights for everything they screen or display in class.

To add to that confusion, colleges and universities often adopt internal rules for faculty that allow less freedom to display films and videos than is probably allowed by the law. Due to widespread confusion, as well as a lack of clarity in legal doctrine, the guidelines state, "it is unsurprising that academic gate keepers (libraries, university general counsels, IT staffs, etc.) frequently choose to adopt overly cautious and conservative copyright policies that sometimes result in a diminished educational experience for film and media students."

Other institutions, meanwhile, don't distinguish between print and visual materials. Columbia University's statement on the use of copyrighted works by faculty and staff explicitly discusses only written documents. But even faculty at institutions that do have such guidelines -- such as the University of California at Los Angeles, which has a well-regarded film school -- might not be aware of the rules.

"I’m sure they have some kind of guidelines, but I haven’t seen them. I wouldn’t doubt it," said Jan-Christopher Horak, a visiting professor at UCLA's School of Theater, Film and Television and a distinguished film curator.

For now, Mittell is focusing on two issues that are still far from settled:

• Cinema and media scholars were able to win an exception last year to the Digital Millennium Copyright Act of 1998 that allows instructors to legally violate copy protection "for the purpose of making compilations of portions of those works for educational use in the classroom," according to the film society's guidelines. That would allow a professor to copy scenes from DVDs, for example, and screen them in a montage for a class. The exception expires in 2009, however, and Mittell sees it as an opportunity to lobby for a clarification that would allow scholars to use source materials from the main university library, for example, instead of only "the educational library of a college or university’s film or media studies department," as currently mandated.
• Educational allowances for fair use currently only apply to instructors, but for students who may increasingly find themselves needing to use film or media clips for class presentations, copyright protections still apply. The result, Mittell has found, is that much of the class period is often spent cuing DVDs to specific scenes instead of using a mixtape-style disc with the needed clips in the right order. "What you effectively have to do is run over some time [in the class period] in order to cue it up to the place where you want," he said.

The society's next policy document will tackle another issue that has caused confusion among media researchers: what limits fair use imposes on publishing clips in online journals, DVDs enclosed with published articles, Web sites and other digital scholarly venues.