Ponder the difference between the comedian and the musician. Both create and perform works to entertain audiences, but they go about protecting that work in different ways. The notoriously litigious music industry often resorts to the legal system to protect itself from pirates and samplers. But comedians don't. So why hasn't the joke well gone dry?

That's the question asked by a forthcoming book chapter from the University of Chicago Press called "Intellectual Property Norms in Stand-Up Comedy." Written by Dotan Oliar and Christopher Jon Sprigman of the University of Virginia School of Law, the chapter offers a case study in the axiom that more IP rights aren't always better IP rights.

For comedians, ripping off a joke is a major sin, but such cases almost never end up in court. Federal court, where copyright cases are heard, is too expensive to be worth it. Besides, copyright law only protects the exact expression, not the idea, so rip-off artists who add some different details are free to do so.

This hasn't led to a dearth of jokes. Instead, comedians use social norms rather than law to enforce their joke rights, and these social IP norms have actually been part of the process that shifted comedy away from one-liners and "rim shot" jokes to today's long-form observational comedy.

The authors interviewed 19 working comedians in detail, and they came away with an understanding that creators don't necessarily need formal legal protection to encourage them to create. But when they get protection, even an informal kind, creativity changes in interesting ways.

For instance, early twentieth century vaudeville featured plenty of joke and "bit" theft. Comedic ideas were common property; it was the performance that mattered. But as joke stealing became taboo in the 1950s and '60s, thieves would find themselves blackballed from clubs or ostracized by their fellow comics.

As this protection proved itself to be effective in practice, it encouraged comics to spend more effort on their "text." Jokes were no longer common property, so comics invested both time and money writing (and hiring others to write) new material in a way they rarely did before.

The result was more original comic material—but there was a side effect. "Comedians today invest less in developing the performative aspects of their work," says the chapter. "Indeed, many stand-ups today stand at a microphone, dress simply, and move around very little compared with the more elaborate costuming, mimicry, musicianship, and playacting that characterized the post-Vaudeville comics."

When IP norms did not exist, the hard-to-replicate live performance was the key differentiator. Once the informal community norms offered some protection for jokes, much of the creativity shifted back to the "text" and away from the performance.

In both cases, though, comedy flourished, and neither required official IP laws. "Conventional wisdom would have us believe that this [lack of official protection] entails a tragedy of the commons and suboptimal supply of jokes," write the chapter's authors. "Our research makes us pause. We see an operating market."

Their takeaway is not that we don't need rules, but that we should be doubly vigilant against the "careless expansion of legal protections." Informal norms might work well enough within different communities (and the smaller the community, the easier social norms are to enforce), and changing the official rules could produce unintended changes in the type of creativity that people engage in.

IP rules are needed, but they aren't "necessarily right for stand-up or for every creative practice." And that's no joke.