If you haven't been following my current train of thought, please go back to my Feb 21 posting, A Breed Apart (2), and catch up. Thanks.
The Digital Millenium Copyright Act (DMCA) was passed in the year 2000 to protect the rights of big companies that produce audio, video, movies and games. The law provides strong penalties for many actions that people use to take for granted, such as taking a thing apart and seeing how it works, in order to build a competing thing. That's not the worst part, though. The law was written on the assumption that only a few intended companies would ever use it, and of course, they would always use it judiciously. This law should have been debugged.
Hewlet Packard was the first company to find a serious bug in the DMCA, and they used it to block competition in the printer cartridge business for two years. Details of this case and others are here.
HP's clever idea was to prevent other companies from making printer cartridges that would work in their printers. (For many years, you have had a choice of buying HP cartridges, or buying cheaper from competitors.) HP placed a small computer processor in each cartridge and gave it a small program to run. Competitors had to reverse-engineer what this CPU did, in order to produce competing cartridges. Such reverse engineering has, in the past, broken AT&T's monopoly on hopelessly expensive connections to the phone network, and brought down the prices of (IBM compatible) computer hardware. But HP alleged that this reverse engineering is illegal according to the DMCA. We are lucky that eventually they lost this case; the technical issues at law were complex and not easy to call.