It's a new US law that was passed in October of 1998. A part of this legislation makes it illegal
to "circumvent a technical measure that effectively controls access to a copyrighted work."
You may be asking, "What should I care? Besides, it's necessary to protect an author's work and promotes the release of creative works."
If by "protect", you mean "makes sure they get paid", then I disagree. There is already a doctrine of law called "right of first sale" that does that. It lets an author decide how and when a creative work is released, and who gets to do it, and in what format. Then comes "compulsory" licensing to provide even more "protection" for the author when somebody else wants to re-release it.
They have plenty of protection. I believe that we should be more interested about protecting OUR rights. Don't forget that there is another one of those pesky doctrines of law, something called "fair use", that affirms the right of the end-user to make other uses of the material. It even applies to situations where that "alternate use" might involve making a copy of the original, purchased copy. That's something that can'tbe done if there is a "technical measure" in place that prevents an "unauthorized by the author" copy from being made.
You ask, "Still, why does Mickey care?
Well, it's because the DMCA thus makes it a crime to reverse engineer anything used to prevent the copy from being made, regardless of what I was intending to do with it. It assumes that I was going to provide a copy of it to the world via the Internet, when actually I was going to play it in my RV. It assumes that my intent was something other than to "protect" my investment from getting stepped on or melting in the heat.
But where I really get annoyed with it is this: It's an attempt to legislate "security through obscurity" so that you're obligated to look away when details of the "technical measure" are made known. It goes further, to make it wrong to even take a peek at the inner workings of a "protection measure", much less talk about it.
It affects me and my family, because I pay our bills with income from an electronic engineer's position. A large percentage of the knowledge I have used in my past work has come from reverse-engineering. It's one of the things that I do best. Compared to formal education, I have many more years invested in hobbyist-style experimentation. And I can think of several occasions where the task at hand involved the "circumvention of a technical measure."
That's why my issue is this:
It can now be illegal to decode a filesystem, remove a tamper-resistant screw, or even to use WinZip to open a self-extracting executable. Whatever the original author chooses to call their "technical measure" is sufficient.
It also sets a precedent, in that it creates a new class of intellectual property. To date, there have been copyrights, patents, and trade secrets. Now there is a new category that appears to be called "protection measures." It does not have to be disclosed (so it's sort of a trade secret, like why Pepsi can't be sued by Coca-Cola. They didn't steal the secret formula, they reverse-engineered it), but it's not okay to discover it on your own. That make this new category very different from a trade secret.
Additionally, the strength of the protection measure is not important. Don't bother arguing about the definition of "effectively", because, as in the case of DeCSS, that it was easy to break has been shown not to matter to the courts. So, that means that ANY measure will be sufficient. A 1-bit encryption, a funny hole pattern in a fastener, an obscure web-page address: all are "effective".
Here is my favorite analogy of what can happen with this law:
Let's say I am a hot-dog vendor. I make a fine hot-dog and I am very proud of it. In fact, I consider it a work of art. I sell my "works of art" with a plastic wrapper around it. You can buy the hot-dog and take it home. However, to eat it you'll have to remove my plastic "technical measure", and to do that, you'll need additional authority.
Oh, and that only comes with these special scissors that I also sell....