There's been a lot of controversy surrounding Selma, the Martin Luther King Jr. biopic that some have accused of playing loose with historical facts. But one of the strangest things about the film is how it deliberately misquotes the civil rights leader. The legal scholar Jonathan Band writes that this was thanks to copyright law.

Selma director Ava DuVernay may well have taken more license than artistically necessary in the confrontational scenes between Martin Luther King Jr. and President Johnson. But inaccuracies in other significant parts of the film were forced upon DuVernay by copyright law. The film’s numerous scenes of King delivering powerful speeches regarding civil rights all had to be paraphrased, because the MLK estate has already licensed the film rights in those speeches to DreamWorks and Warner Bros., for an MLK biopic Steven Spielberg is slated to produce.

Copyright law has a doctrine called fair use that's supposed to deal with exactly this type of issue. If you want to use small portions of a copyrighted work to create a work of your own, copyright law often allows it without getting permission from the copyright owner. Indeed, I relied on fair use to quote the passage in the previous paragraph.

So why didn't Selma's director rely on fair use to justify quoting small portions of "I Have a Dream" and other classic works by King? Most likely, the problem is that studios are extremely conservative about exercising fair use rights. And they have good reason to be wary.

Fair use is supposed to operate as a safety valve for free expression

If Paramount had distributed a version of Selma that relied on fair use to justify using some King clips, and a court later ruled these uses were not actually fair, it would have been a financial disaster. Paramount could have been on the hook for big damages and could even have been forced to cancel showings of the movie and destroy its inventory of Selma DVDs. And the King estate is famously litigious, having sued both USA Today and CBS for quoting his "I Have a Dream" speech without permission. So rather than take that kind of gamble, studios almost always insist that works be licensed, even if a plausible fair use argument exists.

Fair use is supposed to operate as a safety valve for free expression. Without it, you can wind up giving the descendants of historical figures veto rights over how they are portrayed in print and film. Works that meet with the King family's approval can include excerpts from King's famous speeches, works that don't, can't.

And the King family is far from the only example of an estate using copyright to police how a public figure is depicted. In one famous case, the grandson of James Joyce used legal threats to squelch biographies that cast his grandfather in a negative light.

The ultimate solution, as Band notes, is for copyright terms to be shorter. Prior to 1976, the maximum length for copyright protection was 56 years. If that rule were still in effect, "I have a Dream" would fall into the public domain in 2019. After that, anyone could use the speech without worrying about copyright. But Congress has retroactively extended copyright protection in 1976 and again in 1998. As a result, Band says, King's works won't fall into the public domain until 2039.

It would also be helpful if copyright penalties were less severe. The ability to gain an injunction against further publication of an infringing work, and ordering existing copies destroyed, is a particularly powerful weapon in the hands of copyright holders. Instead, publishers could be required to pay a share of their profits with copyright holders. That would make it easier for publishers to rely on fair use.