The $1 billion lawsuit that Viacom filed against YouTube last year is likely to be the most high-profile legal case that will help define the scope of digital entertainment rights in the U.S.

But it's not the only one winding its way through the courts.

Intellectual property lawyers who worry about the RIAA and other copyright holders putting a stranglehold on digital music and videos are nervously watching a series of court cases that have expanded the definition of distribution licenses.

Any Web site that gives consumers access to digital content are already required to get both a reproduction license from the record company and a public performance license from one of the organizations that represent music publishers.

Now, the courts are accepting the argument that they also need a distribution license, much like a wholesaler who sells hard copies of CDs.

YouTube's top copyright lawyer, Zahavah Levine, told musicians and technologists how these overlapping rights are making it nearly impossible to secure all the rights needed to the tens of thousands of videos uploaded to the site every day.

In this video, Fred von Lohmann, a senior staff attorney with the Electronic Frontier Foundation, told the same audience that the problem could go well beyond YouTube's fight with Viacom.

He used as an example the case of XM Satellite Radio being sued by the RIAA for making music available to listeners who had a recording device in their car, even though they had paid for reproduction and performance licenses.

The trend so far in these rulings is not good for proponents of free digital music, as more courts accept the argument that making digital music available to end users equates to distributing it.

"It troubles me a lot," von Lohmann says.