I wouldn't call this a "new" law, sampling without permission will always get you trouble but...

No DJ or producer is safe:

In a decision affecting Hip-Hop producers and artists, the U.S. Court of Appeals for the Sixth Circuit in Nashville created what it called a "new rule" in copyright law on Sept. 7.

The "new rule" states that Hip-Hop artists must pay for every sample that they use to create their composition -- regardless of the size of the sample or how it has been altered.
[...]
As a Hip-Hop producer, employing samples extensively, and a Ph.D. student in ethnomusicology, Wayne Marshall has a lot to say about the ruling. "It seems that the law is simply out-of-step with common practice at this point, and that's unfortunate -- for it breeds disrespect for the law.

"Historically, the law has had to adapt to cultural practice lest the scales of justice seem tipped. Judges and lawmakers should recognize that technology has changed the way people make and think about music. At any rate, with turntables outselling guitars and music-making software proliferating, I think the cat's out of the bag. Every new ruling is another finger in the dyke."

The sample at issue was two seconds of a guitar, the pitch was lowered from the original, and it was looped. The idea that the law, and copyright in particular, should evolve with the use of content by the popular culture is not new. Copyright law changed dramatically with the invention of the printing press, again when the VCR/Betamax arrived, and it is in a state of flux at the moment because of new digital technologies that make copying easy.

As we know from past experience, content producers have adjusted to "threats" like the VCR by turning them into money making machines by accounting for new technology in their business plans (movie rentals in that case, iTunes now). Unfortunately, when it comes to copyright these days it's all about locking down content, keeping it out of the public domain, and eroding fair use rights. The proposed Induce Act is the latest major example of how big time content producers (RIAA, MPAA) are attempting to keep consumers and artists from utilizing media as they please.

Sampling will get you in trouble, no doubt about that. Using any sample without permission is basically moronic at this point, considering how many legal problems artists have had with it. As the article says, sampling will evolve so that the samples are too difficult to recognize, but it will not stop. Why? Because that's how art is made, like knowledge, it builds from what came before. That's why these sort of decisions are disturbing, they appear to grant a veto over innovation to content producers.

For the rest of the sampled article above see here.

UPDATE: Here are some other articles on this case. An article in the Boston Globe has much more on the background of this case (which involved NWA) and others that have impacted sampling (involving De La Soul, etc.), check it out.

The consensus in the news seems to be that before this case taking a two second sample was fair use, but now any sample, no matter how small, will cost you if you don't get permission.

For up-to-the-minute news coverage of this situation check here.