When I was in my first semester of law school, I was given a short memo assignment involving some principle of Connecticut contract law. I quickly found a case stating the relevant rule of law—every contract needs consideration, or something. But it quoted an earlier case. Being a good historian, I knew I couldn’t just use the more recent case—I had to track this down to its source. So I looked up the earlier case. But that in turn cited an even earlier one for the same rule. So I looked up that one. After about nine or ten iterations of this, I was in the 18th century, and courts were still citing earlier cases, now from English reporters that I couldn’t look up as easily. I gave up, and concluded that legal authority worked differently than historical authority—if an earlier court said it, that’s good enough, no matter where it originated or what the original context was.

The upside of this is that rules can get transmitted from case to case much more efficiently. The downside is that errors can spread just as easily. Take the idea from copyright law that contributory infringement liability is derived from the tort law concept of enterprise liability. This explanation is widespread in the case law. See, e.g., Perfect 10, Inc. v. Visa Int’l Serv. Ass’n, 494 F.3d 788, 794-95 (9th Cir. 2007); Fonovisa, Inc. v. Cherry Auction, Inc., 76 F.3d 259, 264 (9th Cir. 1996); Intellectual Reserve, Inc. v. Utah Lighthouse Ministry, Inc., 75 F. Supp. 2d 1290, 1293 (D. Utah 1999); Polygram Int’l Pub., Inc. v. Nevada/TIG, Inc., 855 F. Supp. 1314, 1320 (D. Mass. 1994). It’s also featured in the influential Nimmer treatise: “A separate avenue for third-party liability in the copyright sphere is contributory infringement, which forms an outgrowth of the tort concept of enterprise liability,” Nimmer § 12.04[A][3]. And, it’s taught in law schools. The textbook I used to teach copyrights from 2007 through last year used to have only a one-paragraph introduction to secondary liability, followed by cases such as Fonovisa, which included the “enterprise liability” explanation. So, I dutifully repeated it to my students in both copyright and Internet Law, even though I was not really sure what “enterprise liability” was.

It turns out that it is flat wrong. Contributory infringement liability has nothing whatsoever to do with enterprise liability.