The United States Court of Appeals for the Federal Circuit has upheld (pdf) the Creative Commons License as valid, as well as establishing its relationship to copyright law. Basically, if someone uses a work in violation of a Creative Commons license, the license itself vanishes (because it is an additional allowance of use under copyright), and the full copyright restriction becomes the rule by which use is judged and restitution made.
Long live Creative Commons!
found via the Lessig blog
