Of all the areas of practice in the legal field, intellectual property has proved to be one of the most adaptable—and the most challenging. Ideas, after all, are intangible until you develop them into something you can perform, touch, sell, consume, or operate.

Since IP overlaps with so many other fields—technology, art and entertainment, commerce, medicine, marketing—the way attorneys protect it has evolved along with everything else. It’s not always a smooth transition, but it moves along.

On the bumpy side of the journey, intellectual property lawsuits have been some of the most enlightening, expansive, and influential cases in recent history. For every handful of cases that fly under the radar, there are a few landmark lawsuits that have changed the came in terms of the way businesses, brands, and creators traffic in ideas.

Here are three lawsuits that have impacted everything from cannabis products to the art of parody:

RIAA v. Napster (2001)

The Bottom Line: Peer-to-peer file-sharing loses to the music industry but redefines music consumption.

Children of the 80s and 90s, you likely remember this case vividly. In 1999, you probably had Napster on your desktop too, and like millions of other users, you might have happily downloaded a small treasure trove of albums for free. A platform like Napster was a five alarm fire for the music industry, and the Recording Industry Association of Americana (RIAA) promptly sued Napster for allowing users to distribute music they had no rights to—pieces of work whose copyrights were vested with their owners.

The result was nearly eight years of litigation. Napster’s original configuration was ordered to shut down. It emerged later as a paid music service—and the foundation for every streaming service we use today.

Read the RIAA’s insights from the case here.

(Luther) Campbell v. Acuff-Rose Music, Inc. (1994)

The Bottom Line: Hip-hop group 2 Live Crew is responsible for expanding the precedent of fair use—especially for parody works.

You don’t have to look hard to find a copyright infringement case within the music industry, but you may not know about the one that went to the Supreme Court and set the standard what fair use of copyrighted material could look like for parody pieces. When 2 Live Crew failed to get permission from publishing company Acuff-Rose to use Roy Orbison’s “Oh, Pretty Woman” for their new piece, the group released their iteration anyhow: 1989’s “Pretty Woman.”

Acuff-Rose sued to protect the integrity or Orbison’s original work, but the Crew’s attorney, Alan Turn, argued that “Pretty Woman” was a parody of the earlier song. The U.S. District Court for the Middle District of Tennessee ruled in 2 Live Crew’s favor—and after multiple contradictory rulings from other appellate courts, the case made it to the Supreme Court. 2 Live Crew were victorious, and Turk’s argument laid protective groundwork for the SNL sketches and viral YouTube send-ups we know and love.

Read an account of the case by Alan Turk here.

The Hershey Company v. Seattle Conscious Care Cooperative (2014)

The Bottom Line: If your dispensary customers are snack-ish, maybe aim for original treats instead of knocking off a beloved chocolate brand.

When your dispensary’s new product is “Reefers Peanut Butter Cups,” you’re asking for a sour response from one of the world’s sweetest brands. When marijuana was legalized in Colorado and Washington State, purveyors of pot didn’t let their imaginations stop them when it came to product ideas and merchandising. Unfortunately, creating pot-friendly versions of childhood classic treats isn’t the most legally sound way for your brand to enter the commerce arena.

Seattle Conscious Care Cooperative did just that. Hershey sued and eventually settled with SCCC and other dispensaries, who agreed to halt sales of the products in question and do away with remaining inventory. Not only did Hershey’s actions set a firm parameter for a burgeoning industry still taking its first steps, but the case surely prompted future cannabis enterprises to tighten up their branding game as the dispensary space has grown.

Read a run-down of Hershey’s lawsuit here.